Quietly imposing from the outside, this glorious piece of modern Islamic architecture was a gift to the nation from Sultan Qaboos to mark his 30th year of reign. The main prayer hall is breathtakingly beautiful. The Persian carpet alone measures 70m by 60m wide, making it the second-largest hand-loomed Iranian carpet in the world; it took 600 women four years to weave. Mwasalat buses stop outside the mosque. The mosque, which can accommodate 20,000 worshippers, including 750 women in a private musalla (prayer hall), is an active place of worship, particularly for Friday prayers. Visitors are required to dress modestly, covering arms and legs and avoiding tight clothing. Women and girls (aged seven and above) must cover their hair. An abaya (full-length dress) and scarf can be hired from the mosque cafe and gift shop for OR2.5; some form of ID is required as a deposit. Tours are available.