Delhiˇs great Masjid-i Jah?n-Num?, commonly known as the Jama Masjid or Friday Mosque is the largest in the country, with a courtyard capable of holding 25,000 worshippers. It was built in 1644, the last in a series of magnificent architectural achievements by Shah Jahan, the Moghul emperor who also built the Taj Mahal and the Red Fort. The elaborately decorated mosque has three great gateways, four towers and two 40m (131ft) high minarets constructed of alternating bands of red sandstone and white marble. Non-Muslims are welcome to visit the mosque but preferably not during prayer times; revealing clothing is not permitted within the precincts.