Piazza San Marco
"The drawing room of Europe" is how Napoleon is said to have described Piazza San Marco, or St. Mark's Square. Today, make that the drawing room of the world, but it's as spectacular as ever, with its grand colonnades, 18th-century tea rooms, a hulking brick bell tower, and the domed Basilica of San Marco presiding over it all. Take the elevator to the top of the campanile (bell tower) for a bird's eye view, and then head into the basilica, which glitters with wall-to-wall mosaics. Don't miss the Pala d'Oro, a gold-clad altarpiece studded with precious jewels (access costs $3.20).