The Koules (Greek: Κούλες) or Castello a Mare ("Fort on the Sea" in Italian) is a fortress located at the entrance of the old port of Heraklion, Crete, Greece.

Eventually, the Byzantine tower was demolished in 1523, and the Castello a Mare began to be built instead.

Old ships were filled with stone, and were sunk to form a breakwater and increase the area of the platform on which the fortress was built.

[2] During the 21-year long Siege of Candia, Ottoman batteries easily neutralized the fort's firepower.

They built a small fort known as Little Koules on the landward side, but this was demolished in 1936 while the city was being "modernized".