Venice, Palazzo Ducale
If there is a more breathtaking view than walking out of the ticket area into the Palazzo Ducale courtyard just off of the Piazza San Marco, then... I will eat (a delicious piece of cake in the shape of) my hat. The Doge's Palace is often overrun with tourists, but with good reason: it is truly a must-see destination. It's a glorious mix of late-medieval and renaissance architectures in ways that only Venice could devise.