Hagia Sophia (from the Greek: Ἁγία Σοφία, “Holy Wisdom”; Latin: Sancta Sophia or Sancta Sapientia; Turkish: Ayasofya) is a former Greek Orthodox patriarchal basilica (church), later an imperial mosque, and now a museum in Istanbul, Turkey.
From the date of its construction in 537 until 1453, it served as an Eastern Orthodox cathedral and seat of the Patriarchate of Constantinople, except between 1204 and 1261, when it was converted to a Roman Catholic cathedral under the Latin Empire.
The building was a mosque from 29 May 1453 until 1931. It was then secularized by Ataturk and opened as a museum on 1 February 1935.
About 100m away is the Sultan Ahmed Mosque (Turkish: Sultan Ahmet Camii). The mosque is popularly known as the Blue Mosque for the blue tiles adorning the walls of its interior.
It was built from 1609 to 1616, during the rule of Ahmed I. Its Külliye contains a tomb of the founder, a madrasah and a hospice. The Sultan Ahmed Mosque is still popularly used as a mosque.
The Sultan Ahmed Mosque has one main dome, six minarets, and eight secondary domes. The design is the culmination of two centuries of both Ottoman mosque development. It incorporates some Byzantine elements of the neighboring Hagia Sophia with traditional Islamic architecture and is considered to be the last great mosque of the classical period. The architect, Sedefkâr Mehmed Ağa, synthesized the ideas of his master Sinan, aiming for overwhelming size, majesty and splendour.