Don't be deceived by the beauty of the exterior of the Doge's Palace, Piazza San Marco, for justice was served decidedly brutally here, particularly for the crime of treason. The seat of the supreme rulers of the Venetian empire until 1797, Palazzo Ducale is a wonderful example of Venetian Gothic architecture, where every column is different. An awesome sight even from an exterior glance, the two possible tours reveal at least some of the layers of history, the standard tour leading the (literally) hourdes of visitors (over one million in 2010) through rooms of painted ceilings, featuring paintings by Titian, Tintoretto and Veronese, majestic staircases and the grave bridge of sighs, where prisoners would take their last walk to their fate. Of course, each room also has its secret passageways, prison cells and there's even a torture chamber, the secret tour opening these up to our modern gaze. The great seducer, Casanova, was the first to break this gargantuous bastion of power, escaping from one of the prisons. The palace has been open as a museum since 1923.