After you've tried all the museums and tours, you wonder what there is left to see in the city. The Hillwood Mansion, tucked away near Rock Creek Park in Northwest DC, is a welcome treat for those who think they've seen it all. Formerly the home of Post Cereal heiress Marjorie Merriweather Post, the mansion and surrounding gardens offer a look into what high society was like in the 1950s and 60s. She amassed a large french and russian antiques collection, so you'll see paintings and personal affects formerly owned by Peter the Great and Marie Antoinette. You need to call ahead to arrange a tour.