This handsome shopping center, inside a historic 19th-century post office building, hasn't grown into the popular spot that developers hoped it would after renovation in the 1980s. Plans are afoot to convert the space into a hotel or other enterprise, but until that happens, you can enjoy about a dozen food vendors and 17 shops. An observation deck in the building's clock tower offers an excellent view of the city. You'll need a photo ID to get into the building, which also houses federal offices. Metro: Federal Triangle.