The decorated trees at the Carnegie Museum of Art feature a World's Fair theme this year, and three of them, above, from left, are Hats of the World's Fairs; Decorative Arts of the World's Fairs, and Expo 67 — Race to Space. Below is a detail from the Architectural Icons of the World's Fairs tree.

PITTSBURGH — For the 51st year, the Carnegie Museum of Art's Hall of Architecture dazzles with seven, 20-foot trees flanking the museum's perennial favorite, the Neapolitan presepio, an 18th-century Nativity.

Each tree is decorated in the theme of world's fairs, celebrating the exhibit “Inventing the Modern World: Decorative Arts at the World's Fairs, 1851–1939” now on view in the Heinz Galleries of the art museum.

Groups that decorated this year's trees included the Women's Committee of Carnegie Museum of Art, Carnegie Libraries of Pittsburgh, Andy Warhol Museum, Pittsburgh Parks Conservancy, and Frick Art & Historical Center.

Part of the display, the museum's Neapolitan presepio is one of the finest Nativity scenes of its kind and has been a Pittsburgh holiday tradition since 1957.

Handcrafted between 1700 and 1830, the scene teems with lifelike figures and colorful details that re-create the Nativity within a detailed panorama of 18th-century Italian village life. More than 100 superbly modeled human and angelic figures, along with animals, accessories, and architectural elements, cover 250 square feet and create a memorable depiction of the Nativity.

Programs associated with the holiday display include:

Family Singalong with Frank Cappelli, 2 to 4 p.m. Saturday.

Drop-in Tours, noon to 12:30 p.m. each day except 12:15 to 12:45 Sundays through Jan. 6

Winter in the Discovery Room, 1 to 3 p.m. Tuesdays through Fridays, 10 a.m. to 4 p.m. Saturdays, and 1 to 4 p.m. Sundays.

Regular museum hours are 10 a.m. to 5 p.m. Tuesdays through Saturdays, with additional hours until 8 p.m. Thursdays, and noon to 5 p.m. Sundays. For the holidays, the museum will be closed Monday, Tuesday and Jan. 1 but will be open Dec. 31.

Admission, which includes the Carnegie Museum of Natural History, is $17.95 for adults, $14.95 for senior citizens age 65 and older, $11.95 for students with ID and children ages 3 to 18, and free for children younger than 3. Call 412-622-3131 or visit www.cmoa.org.