The norias of Hama are enormous wooden waterwheels mounted on the Orontes River, used for centuries to lift water into aqueducts supplying the city's gardens and farms. Seventeen survive; the largest, at the Four Norias of Bichriyat in a riverside park near the centre, stand 27 metres in diameter — among the biggest wooden waterwheels ever built. Their continuous groaning and creaking, caused by wooden compartments scraping against the millstone, is the defining sound of the city, audible from the surrounding streets day and night.
The wheels themselves are thought to date in their current form to the Ayyubid and Mamluk periods, from the 12th to 14th centuries, though noria-style irrigation on the Orontes goes back to at least the Roman era. Each wheel is built entirely from wood — no nails — and held together by a system of interlocking joints. Traditionally the city's guilds maintained them collectively, and repair was a matter of civic pride. The aqueduct troughs running from the tops of the wheels fed water to specific districts, mosques, and gardens, their allocations governed by a body of medieval water law that settled disputes over who could draw how much and when.