Palatul Cotroceni
The Cotroceni, which incorporates French, Romanian, Art Nouveau, and other styles of architecture, was constructed in the late 19th century as the home of Romania's royal family. After a devastating 1977 earthquake, it was rebuilt and now houses the official residence of the Romanian president. The lavish furnishings, art, and personal effects afford a glimpse into the lives of Romania's former royalty. Guides are required (no extra charge) for the one-hour tour, but you must call ahead to reserve a tour. Since the palace is a bit removed from other sights, you might want to take the Metro to the Politehnica station or simply take a taxi.