The Rawda Island Nilometer was built in 861 on the order of the Abbasid Caliph al-Mutawakkil. Tracking the annual flood helped authorities prepare canals and dykes, anticipate agricultural conditions and manage taxation. A graduated marble column stands inside the stone-lined well, with inscriptions and measuring marks visible as a stair descends around it.
This is very different from a conventional museum: you enter a piece of working infrastructure more than a thousand years old. Descending into the well makes its original function immediate and turns the idea of measuring the Nile into something you can physically see and understand.
