The White Tower of Thessaloniki, is a monument and museum on the waterfront of the city of Thessaloniki, capital of the region of Macedonia in northern Greece. The present tower replaced an old Byzantine fortification which was mentioned around the 12th century and reconstructed by the Ottomans to fortify the city's harbour; it became a notorious prison and scene of mass executions during the period of Ottoman rule. It was substantially remodeled and its exterior was whitewashed after Greece gained control of the city in 1912. It has been adopted as the symbol of the city.