 The city was subjected to four notable sieges in 1537, 1571, 1573 and 1716, in which the strength of the city defenses asserted itself time after time, mainly because of the effectiveness of the powerful Venetian fortifications.Will Durant claimed that Corfu owed to the Republic of Venice the fact that it was the only part of Greece never conquered by the Ottomans.In 2007, the old town of the city was inscribed on the UNESCO World Heritage List.