4. New York City
If you think the Big Apple is beyond your budget, think again. You can stay in well-priced chain hotels (with complimentary breakfast) just steps from the city's top sights, and get around cheaply and quickly by subway or bus. Many of the city's attractions are free, including the urban esplanade known as the High Line; the Smithsonian's Museum of the American Indian; the elegant New York Public Library; and the incredibly moving 9/11 Memorial. And for fast, cheap eats, you can't beat a $1 slice of pizza or a genuine NYC bagel.
Venice may not be the world's most affordable travel location, but you can drink in many of its celebrated sights for free. You'll find moderately priced hotels and B&Bs in the Cannaregio neighborhood and on the Lido, a beachy island 10 minutes from Venice. It costs nothing to stroll and comb the city's storied calli (streets) and canals. Tour the splendid cathedral interiors of the Basilica di San Marco and Basilica di Santa Maria della Salute for free. Dine like the Venetians do in casual neighborhood cafes and bacari (bars) on delicious, inexpensive tramezzini (filled triangular mini-sandwiches) orcicchetti (tapas-style finger foods).