THIS GRAND MOSQUE, with three imposing black and white marble domes, and twin minarets framing its great central arch, was built in 1656 by the Emperor Shah Jahan, on a natural mound. It took six years and 5,000 workers to construct, at a cost of nearly a million rupees. A magnificent flight of sandstone steps leads to the great arched entrances. In Aurangzeb’s time, the area attracted horse sellers and jugglers; today, shoe minders and beggars mill around. The huge 28-m (92-ft) square courtyard can accommodate up to 20,000 people at Friday prayer sessions and at Id, when it looks like a sea of worshippers. Next to the dukka (water tank) for the ritual ablutions, is the platform where, before loudspeakers took over, a second prayer leader echoed the imam’s words and actions for worshippers too far from the pulpit for a clear view.