Istanbul's oldest surviving church, St John of Studius, is now a mere shell consisting only of its outer walls. However, you can still get an idea of the original beaut)' of what was once part of an important Byzantine institution.
The church was completed in AD 463 by Studius, a Roman patrician who served as consul during the reign of Emperor Marcian (450-57). Originally connected to the most powerful monastery in the Byzantine Empire, in the late 8th century it was a spiritual and intellectual centre under the rule of Abbot Theodore, who was buried in the church's garden. The abbot is venerated today in the Greek Orthodox Church as St Theodore.

Until its removal by the soldiers of the Fourth Crusade , the most sacred relic housed in the church was the head of St John the Baptist. The emperor would visit the church each year for the Beheading of the Baptist feast on 29 August.
In the 15th century the church housed a university and was converted into a mosque. The building was abandoned in 1894 when it was severely damaged by an earthquake.

The church is a perfect basilica, with a single apse at the east end, preceded by a narthex and a courtyard. It has a magnificent entrance portal, wilh carved Corinthian capitals and a sculpted architrave and cornice. Inside, it is empty, apart from a colonnade of six columns of verdigris. (s1)