Koules is called the sea fortress located at the entrance of the port of Heraklion and was built by the Venetians. On the ground floor is divided into 26 apartments that served as food and munitions warehouses, but also as prison cells. On the floor there were rooms for the officers along with an oven, a mill and a small church.
On the three sides to the sea they opened boxes for the cannons that protected the harbor. In 1630 there were 18 canons on the ground floor and 25 on the floor. In the north-eastern, western and southern sides, marble reliefs of the feathered lion of Venice have been embossed, which today are preserved amputated. Koules is visited and is also used for cultural events. Periodic restoration work is performed.