In the Shadow of the Sword: The Birth of Islam and the Rise of the Global Arab Empire

The outline of an early mosque found at Be’er Ora, in the Negev Desert. It has two semi-circular architectural features that indicate the direction – the qibla – in which the faithful should pray. The oldest, pointing directly ahead, is oriented towards the east; the later, on the right of the photograph, points towards Mecca. (Tom Holland)