In medieval Egypt, the annual Nile flood was a matter of life and death — the difference between abundance and famine. To manage this vital resource, a network of Nilometers was built to measure the seasonal flood. During the Abbasid period, a new Nilometer was constructed to replace its ailing predecessor. Located on the river island of al-Rawda, across from Fustat in modern-day Cairo, it remained the state-sponsored site of Nile measurement for centuries.

While principally a measuring device, the Nilometer bore a stone-carved Kufic inscription with Quranic verses praising God’s beneficence through rainfall, alongside the Abbasid caliph’s titles. In a rare occurrence in medieval Islamic architecture, the inscription also reportedly included the name of the Nilometer’s architect.

Yet at some point between the end of the ninth and the eleventh centuries, the inscription segment that bore the titles of both caliph and architect was expertly excised and replaced with additional Quranic verses. Why would someone alter such a highly visible, politically significant inscription? What forces were at play?