Next to the modern port of Heraklion, the visitor can admire the small picturesque Venetian harbor, currently serving as a marina with the impressive fortress of Koules that once protected its entrance. The 2km long jetty of the modern port starts here and is one of the favorite walk tours of the citizens.
Opposite Koules, at the point where there is now the café Marina, until the early 20th century a smaller fort was built to protect the other side of the entrance, called Small Koules. In the coastal avenue we can still see the surviving oblong arched shipyards, the tank of Zane (next to the large shipyards), and the salt storage house (between the large and the small shipyards).
The first major port constructions were carried out by the Arabs in the 9th - 10th century, in order to use Heraklion as a base for their pirate raids. The port was also used for the Byzantine Castle of Handax (the name of Heraklion in that era) after 961 AD. During the Venetian era, the port of Candia (as the Venetians called Heraklion) turned to the most important port in the Eastern Mediterranean with the largest export activity. In the 17th century the port could fit 50 galleys and, especially during the Cretan War (against the Turks) the entrance was blocked each night by a huge metal chain. The Venetian exports to Europe included the famous Malvasia wine (one of the most famous wines of that era), salt (mainly from Elounda), honey, cheese, beeswax, silk, raisins, cotton, and olive oil.
During the Ottoman period, the Turks retained the use of this very important harbor. The beautiful harbor however suffered great destructive alterations by the modernization trend of the 20th century, in order to make room from the seaside road and the new port. Most of the shipyards, Small Koules and the Gate of the Molos were demolished. The last gate was built on the starting point of the current pedestrian road of August 25 and controlled the entrance to the harbor.
Heraklion Venetian shipyards 
At the port of Heraklion we see even today part of the shipyards (arsenals) consisting of large elongated domed rooms. They are the shipyards of the Venetians where they housed, stored, constructed and repaired their ships.
Opposite the Great Koules of Heraklion (Rocca al Mare), which still dominates the entrance to the Venetian port of the city, the Turks founded a smaller tower. It was the only fortification work that the Turks added to the harbor area throughout the period of their domination on the island.
Koules Fort (Rocca al Mare) 
The imposing medieval fortress of Koules still stands at the beginning of the western breakwater of the modern port of Heraklion. Its real name is Rocca al Mare, named so by its Venetian founders. Koules, or the Great Koules like it is called, was not the sole ruler of the port.
