Many people associate Dumbarton Oaks, a 19th-century Georgetown mansion named for a Scottish castle, with the 1944 international conference that led to the formation of the United Nations. Today the 16-acre estate is a research center for studies in Byzantine and pre-Columbian art and history, as well as landscape architecture. Its yards, which wind gently down to Rock Creek Ravine, are magical, modeled after European gardens. The pre-Columbian museum, designed by Philip Johnson, is a small gem, and the Byzantine collection is a rich one.

This unusual collection originated with Robert Woods Bliss and his wife, Mildred. In 1940, they turned over their estate, their extensive Byzantine collection, a library of works on Byzantine civilization, and 16 acres (including 10 acres of exquisite formal gardens) to Mr. Bliss's alma mater, Harvard, and provided endowment funds for continuing research in Byzantine studies. In the early 1960s, they also donated their pre-Columbian collection and financed the building of a wing to house it, as well as a second wing for Mrs. Bliss's collection of rare books on landscape gardening. The Byzantine collection includes illuminated manuscripts, a 13th-century icon of St. Peter, mosaics, ivory carvings, a 4th-century sarcophagus, jewelry, and more. The pre-Columbian works feature Olmec jade and serpentine figures, Mayan relief panels, and sculptures of Aztec gods and goddesses.

The historic music room, furnished in European antiques, was the setting for the 1944 Dumbarton Oaks Conversations about the United Nations. It has a painted 16th-century French-style ceiling and an immense 16th-century stone fireplace. Among its notable artworks is El Greco's The Visitation.

Pick up a self-guiding brochure to tour the staggeringly beautiful formal gardens, which include an Orangery, a Rose Garden, wisteria-covered arbors, groves of cherry trees, and magnolias. Unless you're a fan of Byzantine or pre-Columbian art, you're likely to spend more time in the garden, as much as an hour when everything is in bloom. Exit at R Street, turn left, cross an honest-to-goodness Lovers' Lane, and proceed next door to Montrose Park, where you can picnic. There is parking on the street.