National Postal Museum

Owney, a scruffy terrier who rode the mail trains across the country in the 1880s and 1890s, still stands preserved in a glass case at the Smithsonian's National Postal Museum. He is one of many surprises in a museum that tells American history through the mail. It occupies the former Washington City Post Office, a grand Beaux-Arts building designed by Daniel Burnham's firm and completed in 1914, beside Union Station.

The museum opened in 1993. Its soaring atrium holds vintage mail planes suspended overhead, along with a railway mail car, a stagecoach and other vehicles that carried letters across the country. The galleries cover the Pony Express, airmail pioneers and the everyday work of delivery. Among the curiosities is the wrapper in which the Hope Diamond was mailed to the Smithsonian.

Stamp collectors come for the William H. Gross Stamp Gallery, which displays rarities from one of the world's great philatelic collections, including the famous Inverted Jenny.