On Registan Square, across from the citadel, the Bolo Haouz Mosque stands reflected in the octagonal pool that gave it its name. This is where the khan would come when the mullah gave the call to prayer from the top of the adjacent small brick minaret. No fewer than 20 carved columns support the wooden ceiling of the iwan, whose coffering is extravagantly decorated and stained with warm colours. At 12m, it is one of the tallest in Central Asia.