The history of this complex is fascinating and serves as a capsule summary of Istanbul. It was originally constructed from 532 to 537 under the rule of Justinian. The names credited as the architects were Anthemius of Tralles and Isodorus of Miletus. Much of the original massive dome collapsed in 558, but under the direction of Isodorus the Younger was reconstructed with much more reinforcement in 563. The interiors displayed delicate golden mosaics depicting Christian figures and scenes. That all changed in 1453, when the Hagia Sophia was converted from a church to a mosque by Sultan Mehmet II. The original decorations were covered up, and enormous round plaques called levhas inscribed with ornate Muslim calligraphy were added to the interiors. Minarets were added to the exterior to forever change the look to what we are now familiar with.
The Hagia Sophia evolved into a museum in 1934, as it is no longer an active mosque. The main entrance is off the Aya Sofya Medyani square, a hub for buses, taxis, ATM's, souvenir hawkers, and more. The entrance fee is a steep 15 million Turkish lira (about ten US dollars during my September 2003 stay), but your ticket is a nice little souvenir card. Admire the complicated exterior, whose overall design is not as cohesive as newer mosques like the Blue Mosque but is the established prototype for future structures. Additions to the red-and-gray exterior through the years included minarets and buttressing.
There are plenty of tour groups visiting, but you will hardly notice because of the cavernous spaces. Go inside and have a look upward at the variety of details. The magnificent central dome (100 feet in diameter, 180 feet high), primarily supported by four huge piers, 40 stone ribs and a system of half domes, vaults and buttresses, still is partially supported by a large scaffolding deck that now looks like part of the fabric of the structure (supposedly the scaffolding has been there for over a decade). Climb the ramps to the upper level for a closer look at the brilliant mosaics, which are slowly being recovered from the banishment of years of plaster covering. The impressive marble interiors are a bit dark; so try to use a high-speed film if you are trying to capture these glorious images. The interior columns are crowned by capitals, none of which are alike in design. Peek through some of the windows for intimate views of nearby fountains and domes. Look downwards and marvel at the spaces across and below. The interiors were revamped by a major renovation in 1847-49, which added a delicately gaudy imperial kiosk.
The grounds of Hagia Sophia are almost ignored by visitors, but they include tombs, fountains, a baptistery and a treasury. Once you are outside of the friendly confines of Hagia Sophia, you are fair game for vendors, taxi drivers, touts, etc.