Koules is the name of the sea fortress built by the Venetians in Heraklion. It is located at the entrance to the Venetian harbor, in order to protect the port of Heraklion and, together with the Castle of Paleokastro, the bay of Amoudara from invasions and landings of other conquerors.
It is also known as Castello del Molo, Rocca a Mare, Castle of the Sea, Castle of Candia or former Castel di Candia.
The fortress is built on the western pier of the port of Heraklion, at the northern end of the pier of the old port. It is two-storey and covered approximately 3,600 sq m. Its ground plan is square, with a large semicircular projection on the eastern side. The entrance to the fortress is located on the western side of the fortress, at the end of the pier. A smaller entrance is located on the northeastern side, and led to a semicircular pier, and another on the southern side, towards the port. The fortress is built with massive structures brought from Fraskia and Dia. The outer walls of the fortress are very thick. The thickness on the east, west and northeast sides is 8.7 meters, while on the north side it is about 7 meters. The inner walls are thinner, with a thickness of 1.4 to 3 meters, depending on the location.
Today Koules is open to the public and is also used for cultural events. Periodically, restoration work is carried out and the fortress remains open to the public.