The Dome of Hagia Sophia, Istanbul, Turkey
Hagia Sophia (from the Greek: Ἁγία Σοφία, Holy Wisdom; Latin: Sancta Sophia or Sancta Sapientia; Turkish: Ayasofya) is a former Orthodox patriarchal basilica, later a mosque, and now a museum in Istanbul, Turkey.
From the date of its dedication in 360 until 1453, it served as the Greek Patriarchal cathedral of Constantinople, except between 1204 and 1261, when it was converted to a Roman Catholic cathedral under the Latin Patriarch of Constantinople of the Western Crusader established Latin Empire. The building was a mosque from 29 May 1453 until 1931, when it was secularized. It was opened as a museum on 1 February 1935.
Famous in particular for its massive dome, it is considered the epitome of Byzantine architecture and is said to have changed the history of architecture.
The dome of Hagia Sophia is carried on four concave triangular pendentives, a form which was first fully realized in this building. The pendentives serve to transition from the circular base of the dome to the rectangular base below. These were reinforced with buttresses during Ottoman times, under the guidance of the architect Mimar Sinan.
Another interesting fact about the original structure of the dome was how the architects were able to place forty windows around the base of the dome. Hagia Sophia is famous for the mystical quality of light that reflects everywhere in the interior of the nave, which gives the dome the appearance of hovering above the nave.
It was the largest cathedral in the world for nearly a thousand years, until Seville Cathedral was completed in 1520.
For more information : en.wikipedia.org/wiki/Hagia_Sofia