The mosque of Ibrahim Khan is located almost in the center of the imposing fort Fortezza in Rethymnon. The building was built in 1583, during the Venetian occupation, and functioned as a Christian church dedicated to Saint Nicholas. The cathedral of the city had been destroyed by an invasion in 1571, so the Venetians decided to transfer the worship to a safer place inside the castle of Fortezza. However, it seems that it was not the central temple of the city due to lack of space.
After the Ottomans occupied the city in 1646, the church of Saint Nicholas was converted into a mosque dedicated to the sultan of the Ottoman Empire Ibrahim Khan. Then the large dome of 11m diameter was added, which makes the building stand out from all the other buildings in the fortress.
The building has a square plan with spherical triangles in the corners formed by the arcs on its four walls. Above the entrance there is a relief bow, while the mihrab is decorated with relief patterns. Externally the base of the shattered minaret is preserved.
The precious rainwater for the fort was concentrated in a large tank next to the mosque, meeting the needs for water during the hard siege times.