Always a hit with kids, the National Zoo was founded in 1889 and absorbed into the Smithsonian Institution one year later. The leafy, 163-acre Frederick Law Olmsted–designed grounds in northwest Washington are home to over 400 species—from tiny leaf-cutter ants to four-ton Asian elephants. Late spring, when there are adorable baby animals to coo at (and before the swampy humidity sets in), is the best time to visit. Each April, the zoo celebrates all things panda with films, costumed characters, and keeper talks, but watching bamboo-eating Mei Xiang, Tian Tian, and their cub, Tai Shan, is a big draw year-round. In the Invertebrate Exhibit's touch tank, you can tickle the backs of sea stars, horseshoe crabs, and sometimes shoulder up to giant tarantulas (if you're gutsy enough). Parking is limited, but the Woodley Park–Zoo stop is just a 20-minute metro ride from downtown on the red line.