Agios Markos Church or the Basilica of Saint Mark is located in the central square of El. Venizelos in Heraklion.
Agios Markos Church was built in the early years of Venetian rule (1239) and is dedicated to the patron of the Venetians, Saint Mark.
The basilica was aisled, wooden roof with a characteristic the bell tower with a large clock in the southwest corner. The belfry was a copy of that of Saint Mark in Venice.
During the Turkish occupation, the church was given by Kiopruli to Defterdar Ahmet Pasha, from which it took its name "Defterdar Mosque". The Turks demolished the bell-tower and raised a minaret in its place. Until 1915 it functioned as a mosque.
The church of Saint Mark was badly damaged by various earthquakes. Today, the church with the help of the Archaeological Service has been restored to its original form and is used as a hall for ceremonies, exhibitions and similar spiritual events.
Source: yallou.com