The Walters Art Museum is one of the great small museums in America, and it is entirely free. The collection spans 55 centuries, from ancient Egypt through medieval Europe to 19th-century European and Asian art, with particular strength in medieval manuscripts, Islamic art, and 19th-century French painting.
The building itself — a combination of a Renaissance palace, an ornate gallery wing, and a Victorian mansion — is worth seeing independently of the collections it contains. The Egyptian and Byzantine galleries in the Renaissance wing are highlights. In Mount Vernon, within easy walking distance of the Washington Monument and the Peabody conservatory, making for an excellent neighbourhood afternoon.