The fortifications of Heraklion are a series of defensive walls and other fortifications which surround the city of Heraklion (formerly Candia) in Crete, Greece. The first city walls were built in the Middle Ages, but they were completely rebuilt by the Republic of Venice. The fortifications managed to withstand the longest siege in history for 21 years, before the city fell to the Ottomans in 1669.
Heraklion's fortifications have made it one of the best fortified cities in the Mediterranean. The walls remain largely intact to this day, and they are considered to be among the best preserved Venetian fortifications in Europe.