The church of Hagia Sophia (Greek: Ἁγία Σοφία, meaning "Holy Wisdom" Turkish: Ayasofya), now the Hagia Sophia Museum, is a former Chalcedonian (Greek Orthodox) church located in the city of Trabzon in the north-eastern part of Turkey. It dates back to the 13th century when Trabzon was the capital of the Empire of Trebizond. It is located near the seashore and 2 miles west of the medieval town's limits. It is one of a few Byzantine sites still existent in the area.
Hagia Sophia was built in Trebizond during the reign of Manuel I between 1238 and 1263. After Mehmed II conquered the city in 1461 the church was converted into a mosque and its frescos covered in whitewash. During World War I and for a brief period afterward, the city was occupied by the Russian military and used as a makeshift hospital and depot. Afterwards it was put back into use as a mosque, until 1964 when it was turned into a museum - which it remains to this day. From 1958 to 1964 the frescoes were uncovered and the church consolidated with the help of experts from Edinburgh University and the General Directorate of Foundations.
The Hagia Sophia church is an important example of late Byzantine architecture, being characterised by a high central dome and four large column arches supporting the weight of the dome and ceiling. Below the dome is an Opus sectile pavement of multicolored stones. The church was built with a cross-in-square plan, but with an exterior form that takes the shape of a cross thanks to prominent north and south porches. The structure is 22 metres long, 11.6 metres wide and 12.7 metres tall. The late 13th-century frescos, revealed during the Edinburgh University restoration, illustrate New Testament themes. External stone figurative reliefs and other ornamenting is in keeping with local traditions found in Georgia and Armenia.
24 metres to the west of the church is a tall bell tower, 40 metres high. It was built in 1427 and also contains frescoes.