Little Hagia Sophia

Little Hagia Sophia (Turkish: Küçuk Ayasofya Camii), formerly the Church of the Saints Sergius and Bacchusis, is a former Eastern Orthodox church dedicated to Saints Sergius and Bacchus in Constantinople, later converted into a mosque during the Ottoman Empire.

This Byzantine building with a central dome plan was erected in the 6th century and was a model for the Hagia Sophia, the main church of the Byzantine Empire. It is one of the most important early Byzantine buildings in Istanbul.

Source

 * Aya Sophia ster van Istanboel in 'Assassin's Creed Revelations'