Rock Creek Park

One of the country's earliest, urban national parks, a 2,000-acre wooded oasis following its namesake waterway through the heart of the city. Shady paved trails drawing bikers, jogger, skaters. On weekends and holidays, portions of Beach Drive close to motorized vehicles. Also tennis courts, golf course, stables and planetarium/nature center (W-Su, 9 am-5 pm) with ranger-led tours. Free (fees for some activities).