View from the Pantocrator Bastion to the Bethlehem Bastion guarding the western part of the walls. The Venetian Walls of Heraklion extend to a length of about 4,5 km and form a triangle protecting the "Old Heraklion" of the 16th century.

During the last years of Venetian rule Crete lived under the threat of Turkish invasion. In 1645 began the fifth Veneto-Turkish war. A Turkish army landed in west Crete in that year, and after many hard battles the Turks became lords of the whole island excluding Candia (modern Heraklion) and few isolated strongholds like Gramvousa. The siege of Heraklion was the most dramatic episode in the strife-ridden history of the island, lasting 21 years (1648-1669, the second longest siege in history). In August 1669 General Sea Captain Francesco Morosini, commander of the Venetian forces was left with only 3,600 fit men and scant supplies to defend the fortress. After securing safe passage for the remainder of his army he surrendered to Grand Vizier Ahmed K�pr�l� on 27 September 1669. As part of the negotiations, all Christians were allowed to leave the city with whatever they could carry with them.