United States National Arboretum

Technically a research division of the Agriculture Department, this 446-acre haven always has many more trees than people, even on its busiest days during the spring azalea season. Highlights include a boxwood collection, dwarf conifers, an Asian collection, a herb garden and “herbarium” of dried plants, as well as the National Bonsai Collection, which contains more than 200 trees donated by Japan and is said to be worth something in the order of $5 million. Also on display, somewhat incongruously, are 22 columns removed from the Capitol’s East Front during its 1958 expansion. See the website for details of tram tours, talks and other events such as garden fairs.