The church of Agios Nikolaos, located in Splantzia Square, was built before 1320, during the Venetian period, as a monastery of Dominican Order. After the dominance of Turks in Chania in 1645, the church was transformed into a mosque and was given the name Hiougkar Tzamisi (the Emperor’s mosque), in honour of sultan of the Ottoman Empire, Imbraim.
The sword of the Turk dervish, who was the first one that entered in the city, was considered to be blessed and wonder-working, and was reserved there. Its importance is highlighted by the existence of two- instead of one- balconies on the minaret on the southwest corner of the temple. The morphological elements of the minaret are of great interest, as they follow the Venetian tradition.
Source: chaniatourism.com