Sultanahmet Cami, known to the west as the Blue Mosque, stands next to the ancient hippodrome on the site of the Byzantine palace. It was built in 1609-17 by the architect Mehmet Aga, and was the last and largest of the imperial mosques to be built during the Ottoman era. It is one of the few mosques in the world with 6 minarets, and it has a 22.5m (74ft) diameter dome that nearly equals that of Aya Sofia in size. The dome, which is 43m (141ft) high, is supported by four large fluted columns each measuring 5m (16ft) across.
The main entrance is reached through a spacious courtyard surrounded by granite columns with a hexagonal wrought-iron ablutions fountain at the centre. Visitors, however, should use the side entrance and keep within the partitioned area so as not to disturb worshippers. Head-scarfs and coverings are issued at the door.
