The Colosseum

THE ORIGINAL COLOSSEUM?

It is a well-known axiom among archaeologists that the more famous a monument is, the less likely any of its original structures are to survive – the more likely it is to have been restored, rebuilt and, more or less imaginatively, reconstructed. There is an inverse correlation, in other words, between fame and ‘authenticity’ in the strictest sense. The Colosseum is a classic instance of this rule. A large proportion of what you see when you visit is much later than the original work of Vespasian and Titus in the 70s AD. The puzzle of dating the individual parts and the different phases has kept archaeologists amused for centuries. The truth is, though, that – despite the confident assertions of most guidebooks – it is now impossible in many cases to be certain which bits were built when. The usual euphemism that the ‘skeleton’ of the building is still essentially in its original form may be true enough, but it glosses over the question of how much of the building counts as the skeleton.

The monument has suffered all kinds of damage – from fire, earthquake and other natural and man-made disasters – throughout its history. There are records of repairs up to perhaps as late as the early sixth century AD, commemorated in inscriptions that have been discovered in the building (the latest one documents the restoration of ‘the arena and the podium, which had collapsed in an abominable earthquake’). A particularly devastating blaze in 217 is described by Dio, who claims that the ‘hunting theatre was struck by lightning… and such a conflagration followed that the whole of the upper circuit and every thing in the arena was consumed; and then the rest was ravaged by the flames and dismantled’. The building was, according to Dio, out of use for many years. But even with this clear testimony, it has proved difficult to identify exactly the third-century repairs or their extent. The most recent attempt has concluded that the damage was more limited than Dio implies, but at the same time has suggested that one section of the main outer wall of the building, usually taken to be part of the original first-century construction, actually dates from the rebuild in the third century.

The problem is that dating Roman brickwork and masonry is a tricky art. Some Roman bricks were stamped with makers’ marks in the course of their production and these ‘brick-stamps’ can give (or allow one to deduce) an exact date. Yet, even so, it is often hard to tell whether the dated brick is part of a small repair or the main phase of construction – or even whether an old brick has been used to patch up damage centuries later. And not just in the ancient world itself. The Colosseum has continued to be repaired and adapted ever since. Some of this work used material indistinguishable from that used by Romans or, even more often, reused Roman material that was lying about the site. It is now not always possible, even for experts (though few like to admit it), to tell an eighteenth-century insertion from a fourth-century one. Of course, this sense that the monument is a patchwork of many centuries gives it much of its charm. But it also makes it hard to trace the details of its history.

The other main problem in reconstructing the original monument – whether as it stood at its inauguration in AD 80 or at any later period in the Roman empire – is the simple fact that so much of it has disappeared. True, its silhouette remains a magnificent and imposing presence in the Roman city-scape, and it is especially impressive from the air flying into the airport at Ciampino from the north (sit on the righthand side of the plane). But about two-thirds of its ancient fabric has gone, most of that, as we shall see in Chapter 6, rifled in later periods to provide the building material for medieval and renaissance Rome. Large sections of the building as it now stands are not ancient at all, but the result of restoration over the last two centuries. Outside, half the outer wall has been destroyed; inside, there is no arena floor and no seats survive (the small reconstructed section of seating on the north-east side is a fantasy of the 1930s and gives a misleading impression of the original layout – illustration 20). Besides, the stark, almost industrial, character of the monument today is the result of the loss of almost all of its marble facings, its rich paintings and stuccoes, and the statues that once decorated the exterior arches. A relief sculpture of the Colosseum from a first-century Roman tomb gives a quite different, and probably more accurate, impression of the decorative excess of the building in its original state (illustration 21).

Nonetheless, there is still a lot to be learned from a careful look at the surviving remains. The archaeology of the building in some important respects enriches our understanding of what went on there. Equally the accounts of the shows, the gladiators and the animal hunts we have already discussed help to make sense of the tantalising ruin that is the Colosseum today.

THE COLOSSEUM ABOVE GROUND

However confusing it can appear on the site itself, the basic design of the Colosseum is clear enough from the ground plan (figure 1): a series of concentric circles, leading in from the vast perimeter wall to the space of the arena in the centre. The surviving section of the perimeter wall on the north side (buttressed at each broken end in the nineteenth century) is arranged in four arcaded storeys, each of which corresponds to a floor level on the interior. On the first three storeys are open archways, with half columns in three different orders of architecture, Tuscan on the ground floor, Ionic on the first and Corinthian on the second (a sequence that was admired and often copied in Renaissance buildings). The top storey repeats the Corinthian order, but has small windows rather than open arches. The total height is 48 metres, and in its original extent it is estimated to have used some 100,000 cubic metres of travertine stone, quarried at nearby Tivoli.

At the very highest level of this outer wall are the sockets which were used to attach the awning (the ‘sails’ or ‘vela’) that served to keep the sun off the audience. (If you look up from the inside of the building when the sky is bright blue, these sockets are clearly visible.) It used to be thought – and it is still sometimes said – that the five stone bollards which survive on the ground to the east side of the Colosseum, about 18 metres away from the building, were also connected with the awning system: as if part of a series of giant tent pegs that would originally have extended all round the building and have been used to anchor the ropes of the awnings to the ground. Part of a series they almost certainly were, but they would have been disastrously ill-suited to such a weighty task, as they have no foundations and are simply bedded into the soil. A much better guess is that they played some role in a controlling visitors and access to the building.

Working in from the exterior, we find a series of four circular corridors (usually known in studies of this building as ‘annular corridors’ from the Latin for ‘ring’, ‘anulus’). These give access to different parts of the monument and to the stairways leading up to higher levels as well as offering amenities such as water fountains and, we must assume, lavatories (though, unlike the fountains, no undisputed remains of lavatories have been discovered). These annular corridors supported the structures above, constructed in a mixture of travertine, other local stone and brick. As the cross-section shows (figure 3), the number of corridors decreases as you move further up the building.

There were eighty entranceways into the Colosseum from the outside. The four at the main axes were differentiated from the other seventy-six and it is generally assumed (on some – but frankly not very much – evidence) that these were used by the performers and the emperor and his party or by the officials presenting the show. The two on the long axis to east and west are usually taken to be the performers’ entrance and exit (the best argument for this is the adjacent stairs connecting them with the underground service areas of the Colosseum). Modern scholars (and ground plans) often slap technical-sounding Latin names on them: the ‘Porta Libitinensis’ or ‘Libitinaria’, after the goddess of death, Libitina, at the east, through which dead gladiators were removed; the ‘Porta Triumphalis’ at the west, through which the gladiators are supposed to have entered in procession at the start of the show (alternatively it is known as the ‘Porta Sanivivaria’ (‘Gate of Life’) through which the still living gladiators walked out of the arena at the end of their bout). In fact, there is almost no evidence for any of these names, still less that they were regularly applied at the Colosseum. The term ‘Porta Sanivivaria’, for example, is known only from the story of St Perpetua’s martyrdom in Carthage; ‘Porta Libitinensis’ comes from a single puzzling reference in a late biography of Commodus to the emperor’s helmet being twice taken out (it does not say from where) ‘through the Gate of Libitina’.

Of the two entrances on the shorter axis, normally taken to be used by celebrity spectators, only that on the north survives; but the symmetry of the monument would suggest that it was mirrored on the south. There are still traces at the north of a vestibule that would once have protruded out from the line of the main exterior wall. Putting this evidence together with the first-century sculpture of the Colosseum (illustration 21) and with images on coins allows us to reconstruct a monumental entranceway on each side, topped by a four-horse chariot presumably carrying the emperor. If the Colosseum were one of the key contexts in the city of Rome for the display of the emperor, imperial statues would have been a particularly resonant and appropriate image over these two principal entrances.

Even more striking is the evidence we have for the stucco decoration at the north entrance. Although only a very few fragments are still visible, when they were much better preserved these stuccoes were drawn by Renaissance artists (including Giovanni da Udine, a pupil of Raphael, who based some of his designs for the Villa Madama on them). The exact interpretation of these is not made easier by the fact that different artists depict them rather differently – divergences that may themselves suggest that the stuccoes were not as well preserved in the Renaissance as they appear, or at least that a degree of imagination has gone into these apparently antiquarian documents. Nor is the date certain: perhaps part of the original first-century decoration, more likely part of a later makeover. But whatever they represent and of whatever date, they are precious evidence for the lavish decoration of the building that has now almost entirely disappeared. Other fragments of brightly painted plaster survive from the corridors, on the basis of which it has been tentatively suggested that vivid colours were widely used in the building’s early phases, toned down to something rather less flashy later.

The main principles of the original seating plan are, as we have seen, clear enough: the seats were ranked hierarchically from the ringside to the top of the house. We can also trace on the ground plan the routes that must have led to the different areas of the auditorium (figure 1): senators, for example, would have entered and made straight for the seats on the podium at the front (Route A, and repeated round the building); those sitting at the highest level would have made straight for the stairs (Route B, repeated), without any opportunity to mingle with the aristocrats, and would then have emerged through a balustraded opening into their designated block (some of the late decorations of these balustrades survive). On the other hand, reconstructed cross-sections of the building (like our figure 3), which confidently mark the exact position of the seats and the number of rows, are based on much less firm information than their clear lines would suggest. The simple reason for this is that no seating survives and so all reconstructions are based on a more or less rough guess of what would fit on the skeleton that remains. This problem is especially acute in the elite sections of the building. The podium on which the (movable) senatorial seats rested certainly extended further down than what now appears, to a casual observer, to be the boundary wall of the arena. This is in fact the back wall of a tunnel which carried at least part of the elite seating above it (illustration 20 and figure 3) and probably acted as a service tunnel around the arena’s edge – with openings through its now largely destroyed front wall onto the arena itself. But the exact extent of the senatorial area is uncertain, as is its form: it is sometimes reconstructed as a sloping area, sometimes as stepped. All these uncertainties make an accurate estimate of how many people it could accommodate (p. 111) very difficult.

The most elite seating of all was in the boxes that we assume took pride of place on the north and south sides of the arena, and are regularly illustrated in imaginative versions of the Colosseum from Gérôme to Ridley Scott and beyond (illustration 8, p. 57). Nothing remains of these, but they must have been located at the ringside, approached by the elaborate entranceways at north and south. There is strong evidence to connect the position at the centre of the southern side with the emperor himself, for an underground passageway has been discovered which gave access to the ringside at this key point from somewhere outside the building to the east. About 40 metres of it has been excavated but the starting point has not been identified (figure 1). What is clear, however, is that it was an insertion (possibly under the emperor Domitian soon after the building was opened) into the original structure and that it was elaborately and richly decorated. The walls were originally faced in marble or alabaster, later replaced with frescoed plaster; there was lavish stucco on the vault and in niches; the floor was covered in mosaic. It seems very likely indeed that this passageway gave the emperor private access to his box, in addition to the main entranceway on the ground floor. In fact, its popular name is now ‘the passageway of Commodus’, so called after a story in Dio that Commodus was once attacked by a conspirator ‘in a narrow entrance way’ in the Colosseum – a nice illustration of the emperor’s vulnerability even (or especially) here. If the connection is right, he would have been attacked in his own private corridor, leading to his own ceremonial seat.

If the southern box was for the emperor and his party, what of the northern box? Different scholars and different tourist guides come up with plausible, and not so plausible, ideas. Some imagine that it might have provided overflow accommodation for minor royals and hangers-on. Others suggest that this would have provided suitable accommodation for the Vestal Virgins (whom Gérôme chose to put next to the emperor). It could also have provided for magistrates, particularly those sponsoring the shows. No one knows. And, in any case, it might not always have been used by the same people, or even used at all.

Ancient spectators, sitting in any of these locations, would have enjoyed a view quite different from that offered to the modern visitor. Over the complicated web of foundations that we now see would once have been a wooden floor (not unlike the small section inserted by the Italian Antiquities Service (illustration 20) to help visitors more easily imagine the original appearance. The ancient flooring would have been covered with sand (‘harena’ in Latin, hence the modern word ‘arena’) whether to prevent slippage, or soak up the blood and the urine, or both. But the security of the spectators must have been as big an issue as the general salubriousness (or otherwise) of the fighting space. There would have been something in the order of a 4 metre drop between the senatorial seating and the arena floor, but that might seem rather close for comfort in the face of a couple of angry elephants. Almost certainly there were more safety measures in place. A graffito found during nineteenth-century excavations in the Colosseum has been (rather optimistically, we feel) interpreted as a picture of latticework balustrading around the senatorial podium; but, in any case, there must have been some kind of further barrier in that position, whether in this form or not. Roman ingenuity, however, could do better than that. The two rustics, whose visit to an earlier amphitheatre was the subject of an elegantly whimsical poem in the reign of Nero (p. 38), pick out the clever device designed to keep the animals away from the spectators. This seems to have involved sets of ivory inlaid rollers around the edge of the arena, which would prevent any animals (or vengeful gladiator, for that matter) getting a foothold, and an extra fence laid some way into the arena, with a net (a golden net in the poem) spread out from it to the podium where the elite were sitting. It is often assumed that some such devices would have been used in the Colosseum too. Much as they appreciated their ringside view, the Roman aristocracy were no doubt as keen on self-preservation as we are, and suitably cautious.

THE COLOSSEUM BELOW GROUND

Confronting the modern visitor to the Colosseum, at the heart of the building, is a mass of subterranean walls, which have been the subject of intense debate and sometimes bitter controversy since they were first re-discovered in the early nineteenth century (although it was not until more than fifty years later that any of them went on permanent display). All kinds of issues have been argued over: the date of their construction and their different phases, the exact function of the different parts and (as we explained in Chapter 3) the implications of all this for the question of whether or not the inaugural celebrations of the building in AD 80 could possibly have featured a mock sea battle. But before we explore some of the details of these arguments, and in particular the colourful controversies that seethed over a few years in the early nineteenth century, it is worth considering briefly those aspects of this subterranean world of brick masonry that are not (or not much) in dispute. For the minor details have often swamped more basic, but more important, conclusions.

What is now for us the centrepiece of the monument is ‘below stage’. It is an area larger than the arena itself, if only because at each end of the major axis there are storerooms and (at the east) a corridor leading underground directly to one of the main gladiatorial training camps, with its own practice arena, known as the Ludus Magnus (literally the ‘Big camp’). It is a maze of corridors and hoists which once brought caged animals to the surface via trapdoors in the wooden floor. Stage scenery, which might transform the arena into a world of make-believe, could also be lifted in this way. It is still possible to see the rope burns in the stone edges of some of the lift wells; and archaeologists have uncovered a few of the bronze fittings which held the revolving capstans which were integral to the hoisting machinery. A clever system it certainly is (though exactly how a hippopotamus would have fitted in is hard to imagine); but this must also have been a truly horrible underground world. The maze of corridors would have been dimly lit by skylights at the edge of the arena, and elsewhere by smoking oil lamps. It does not take much imagination to see that this must have been a hive of sweating labour: slaves, skilled stage-hands, animal trainers, hunters, wild animals in their cages, chained criminals and presumably some of the gladiators, all packed together in tiny cells and passages. Above they would have heard the awful thudding of the hunts and contests. Today the noise of just tourists above, ambling across the reconstructed section of floor, is bad enough (although, as these areas are not usually open to the public, most visitors do not have the pleasure of sharing this terror). An elephant or two is hard to contemplate. This was a hell-hole.

Most of the hoisting shafts visible today date from around 300, with some later repairs. The current orthodoxy is that the original plan did not include any such system occupying the area under the arena, and that during the reign of Titus animals would have been let into the arena using hoists fixed on the perimeter wall – or even from the service tunnel under the senatorial podium. The first versions of these major substructures are generally thought now to date from the reign of Titus’ successor, Domitian. But this is what the controversy has been about.

The subterranean structures first began to be systematically uncovered by Napoleon’s archaeologists, working with the Pope’s archaeological team, during the French occupation of Rome between 1811 and 1814; though they had not reached the bottom of the area beneath the arena before the work was stopped by flooding. Nonetheless, even these partial discoveries prompted a furious row and angry exchanges of pamphlets between leading scholars (sometimes hiding behind unlikely pen names) that were satirised in cartoons of the time. There were three main parties. The first was the papal archaeologist, Carlo Fea, who is now probably best known for producing an Italian edition of J. J. Wincklemann’s History of Art, still widely used. Fea argued that the substructures that had been revealed were not ancient at all, but medieval, and that the original surface of the arena had not therefore been on top of these substructures, but underneath them several metres below the level of the seating; this was the only way, he argued, that it was possible to conceive of a naval battle in the Colosseum, as Dio’s testimony demanded, which would not have been feasible with all those masonry insertions. Against him, an architect, Pietro Bianchi, and the Professor of Archaeology at the University of Rome, Lorenzo Re, contended that the substructures were contemporary with the original building (they were, after all, aligned with it) and that the arena floor had been laid on top of them. In support of this they pointed out that, if the fights had taken place at the low level Fea suggested, then great swathes of the arena would have been out of the line of sight of many in the audience, who would not have been able to see into what was to all intents and purposes a pit. They also relied on the evidence of the late Roman inscription commemorating the repair of the arena after an earthquake (p. 123) – for only if it had been elevated on brick and masonry supports could it have been destroyed by an earthquake. As for Dio’s claim about a naval battle, he must have been wrong; Bianchi and Re preferred to follow the evidence of Suetonius who, as we saw (p. 43), located the naval battle elsewhere. The final player was a Spanish priest and antiquarian, Juan Masdeu, who tried to steer a middle path, casting himself as a ‘pacifier’ of the warring factions. He judged that Fea was correct on the original form of the Colosseum, but that the substructures had been inserted in the later third century and the arena floor raised to go on top of them only then. So Dio could have been right about a naval battle there in AD 80.

In many of these old archaeological arguments one suspects that, if one had been a participant oneself, one would have been on what is now seen to be the wrong side. It frankly would have seemed far more sensible to dismiss this warren of walls as a medieval insert and to imagine all the activity in the Colosseum – land- or water-based – taking place on the firm ground underneath it (after all, because of the flooding which put a stop to the excavations, Fea did not know exactly how deep the substructures went). An arena floor perched on a web of rough masonry would have seemed a very odd idea indeed. We have a strong feeling that in 1814 we would have been with Fea (just as we would probably have been with the Cambridge Professor of Greek Richard Jebb, who at the end of the nineteenth century dismissed some of the prehistoric remains excavated by Heinrich Schliemann at Mycenae as a Byzantine slum). But whatever the strength of the arguments on all the different sides, this Colosseum controversy is distinctive for highlighting the problems of interpreting the building that have not significantly changed over 200 years. The issue still is how do you stitch together the different forms of evidence – literary, archaeological, as well as ‘common sense’ views of how the building must have been used – which do not actually quite fit. Can you massage away the contradictions? With all our more extensive knowledge of the structure of the Colosseum and more sophisticated archaeological dating techniques, the modern orthodoxy is still a version of the Pacifier’s compromise: that the substructures are ancient, but were not in place at the very beginning of the building’s history. The arena floor was elevated at its current height, but more simply – so allowing Dio’s claim about naval battles to be right.

But was Dio right? For all the up-to-date careful analysis and new discoveries (including what appear to be patches of waterproofing on the surfaces of the cavity below the level of the arena), we still do not know. It partly depends on how grandly to interpret the spectacular Dio refers to: large boats manoeuvring on a substantial depth of water, or a rather more Toy Town affair in an overgrown paddling pool? But more than that, it depends on a good answer to the question of water supply. Even with the paddling-pool model, we are not sure how the space of the arena could have been filled with water, and drained again, at reasonable speed. One suggestion, which involves using sluice-gates and backflow water from the Tiber, would also have had the effect of bringing quantities of sewage into the arena along with the water. Hardly the image of lavish and luxurious spectacle that Martial’s poetry would have us believe. Certainly a naval battle with a difference.

PLANS AND SPECIFICATIONS

For the design of the Colosseum, water was mainly a problem in a quite different sense. It may be hard to see now how any spectacular sequences of flooding and draining were arranged for the shows. But on a day-to-day basis the pressing issue was how to prevent the Colosseum as a whole, constructed as it was in a river valley, reverting to the lake that the site had been under the emperor Nero. Besides, the building itself acts as a huge water barrel: rainfall on the seating and arena, sometimes torrential, has to be drained away, otherwise up to 175 litres of water a second would accumulate during a heavy storm. One of the most extraordinary – albeit unseen – achievements of the Colosseum’s designers is to have arranged the drainage. Recent archaeological work on the water system has revealed an intricate network of underground drains, around and through the centre of the monument. The ring drain in fact runs 8 metres below the valley floor and takes the water off to flow into the Tiber. Before they even thought about the foundations, the designers had expertly arranged the site’s hydraulics. Obvious as it is, this raises the question of the architectural and constructional skills necessary for such a huge enterprise. Or to put it as most visitors would when they confront this vast structure: how on earth did the Romans build it?

The usual answer is to stress the combination of vast quantities of slave labour (skilled and unskilled), long traditions of practical craftsmanship and a high level of technical and theoretical architectural expertise on the part of the principal designers. That is broadly correct. We can deduce from a minute examination of the Colosseum’s structure and dimensions how an over-arching plan of considerable sophistication (though, at the same time, drawing heavily on traditional designs) was executed by teams of more or less expert workmen.

Part of the trick was to use, and adapt, relatively simple ratios and standard units. It seems that the ideal ratio of length to width for the arena itself was 5:3. According to one plausible recent reconstruction, the original plan for the Colosseum was to have an arena 300 Roman feet long by 180 Roman feet wide. The convention, as we can observe in other amphitheatres, was to make the width of the auditorium equal to the width of the arena, which would have given a total length of 660 Roman feet (300 + 360), a total width of 540 Roman feet (180 + 360) and a circumference to the whole building of 1885 Roman feet – as an architect could have calculated through relatively simple trigonometry. Did this matter? Yes, because the size of the perimeter intimately affects the design and number of the external arches. A grand amphitheatre had to have a number of grand entrances and the convention, it seems, was for the arches of those entrances to be 20 Roman feet wide (a convention that would have made it easier to instruct the artisans). The Colosseum was to have eighty arches, which – if the 20-Roman-foot standard was to be preserved and allowing for the width of the columns themselves – meant reducing the perimeter slightly, to 1835 Roman feet. This was achieved by leaving the size of the auditorium, and so of the audience capacity, intact, but reducing the size of the arena to 2802 × 168 Roman feet (still in the ratio 5:3). In other words, the architects balanced the need for size and scale against the desire to work to simple and familiar ratios and intervals.

This meant that on the ground they could leave teams of artisans and their foremen with a clear plan, which would not need much hands-on supervision from the overall designer. We can see by examining the individual arches on the exterior how much the details of execution could vary from example to example. The vertical jointing patterns are quite different from pier to pier, presumably reflecting variety in the size of travertine blocks delivered from the quarries or sawn on site, and measurements that were not crucial to the overall structure could differ from arch to arch by as much as several centimetres. Likewise it seems that in the design and building of the stairways, the individual teams and perhaps under-architects had a good deal of independence. On the other hand, the voussoirs in the arches – crucial to the stability of the structure – are close to identical, and the outermost annular corridor on the ground floor is 5 metres wide and varies along its entire length by less than 1 per cent. Where it mattered, Roman architects or their design team could ensure absolute precision from their workforce.

So far, so good. But this reconstruction of the principles of working methods tends to conceal how little we know about the identity of those who designed the building: the myth about the architect being a Christian by the name of Gaudentius is just that, a myth; we have no clue who was in charge of the project. It also conceals how little we know about the methods and skills involved in the design. Despite the survival of a first-century architectural handbook by Vitruvius, our understanding of how Roman architects actually went about their work, and what the balance was between traditional practical craftsmanship and highly technical calculations of loading, proportion, lines of sight and so forth, is largely based on guesswork. We have a few traces of ground plans (preserved on inscriptions) and a handful of three-dimensional models of buildings which may have been made by architects to guide the builders on site or to inform (and please) the client. But it is very little to go on. We also read the odd anecdote about architects and their imperial clients, which make various allusions to drawings and plans, as well as to the perilousness of a design career under the emperors. It is said, for example, that Apollodorus, the emperor Trajan’s favourite architect, when explaining some architectural details to his client, was interrupted by the young Hadrian. Unimpressed with the young man’s architectural expertise, he told him brusquely to ‘get back to his stilllifes’. Later, when he had become emperor himself, Hadrian sent to Apollodorus his own plans for a new temple, ‘to show that a great work could come about without his help’. Apollodorus was predictably dismissive of the emperor’s schemes and paid for his candour with his life. What the relationship was between Vespasian and Titus and their anonymous architect – whether or not we should envisage top-level meetings with the clients keenly discussing plans, sketches and models – we can only guess.

There is a sense also in which talk of ratios, units of measurement, traditional craftsmanship and slave labour makes the whole process of construction seem rather too easy. To appreciate the extraordinary scale of the labour, it is worth looking once again at the work and planning involved in those parts of the scheme that were never intended to be visible. For after the complex drainage network, before the building could ever get off the ground, came the foundations.

The Colosseum’s deepest foundations are roughly in the shape of a doughnut. Under the walls and seating they are a full 12 to 13 metres deep, and – for safety’s sake – this depth of underpinning continues for 6 metres outside the perimeter wall, under the pavement. Beneath the arena itself, however, the foundations are shallower, only about 4 metres deep. Simply digging the hole, an oval, about 200 metres × 168 metres and probably 6 metres deep, with pick and shovel was a huge enterprise. It seems likely that some of the excavated earth was used to raise the ground level around the whole building by about 6.5 metres, so that the new amphitheatre stood up proud in its valley setting. (The whole valley floor had already been raised 4 metres with debris from the great fire of Rome in AD 64.) The rest of the spoil from the huge hole, 100,000 cubic metres, that is about 220,000 tonnes of it, had to be carted away in ox-carts, lugging 500 kilos at a time at a speed of less than three kilometres an hour, to the port along the river Tiber. No mechanical diggers, no 30 tonne trucks; only sweat and muscle.

Once the whole area had been excavated, another huge labour began. Two great perimeter walls (one 539 metres, the other 199 metres long), 3 metres thick with a rubble core, 12.5 metres high, retained the solid concrete and rubble foundations. Once the retaining walls had been built, the remaining hole – over 250,000 cubic metres in volume – was filled with concrete, lime, mortar and sand mixed with water and volcanic rock. It is only in the last few years that archaeologists have managed to take core samples from these underpinnings and to establish their make-up and dimension. Much work remains to be done, but the main point is already clear: the Colosseum still stands because it was built on very solid foundations indeed.

Even with all this detail, the scale of the work on just this preliminary phase of construction may still be hard to grasp. In order to bring it rather closer to home we asked a firm of Chartered Quantity Surveyors in 2004 to estimate the costs of creating the Colosseum’s foundations in England then, using modern methods and materials. The specification was as follows:

This is less detailed information than a modern quantity surveyor would normally require. But the provisional estimate we received, which included no drainage work, no professional fees, no VAT, nothing whatsoever above ground – not to mention those elements in the building scheme of which we are unaware or have forgotten to include – was £28.5 million. Of course there is much that cannot be compared (the use of slave rather than wage labour, for a start). None the less, this figure does give a baseline for thinking about the scale of the ancient Roman enterprise.