No photographs can do justice to Angkor -- the stunning, ruined city of sandstone temples and civic monuments from which the Khmer Empire governed much of Southeast Asia for six centuries. But an exhibit opening this Friday at the National Geographic headquarters at 17th and M NW comes close.

The pictures -- there are more than 50 -- are displayed big, in an attempt to convey the scope and grandeur of Angkor. Angkor Wat temple, the largest and best-known of its 72 major structures, is shown from the air and ground. Even on film, it's an unforgettable sight, fitting precisely into forestland and a grid of irrigation canals that its keepers built centuries ago.

A bas-relief of the Churning of the Sea of Milk, a creation allegory from Hindu mythology, brings together hundreds of demons, angels, war elephants, fish, a divine turtle and the god Vishnu. It is depicted in a composite photo running 50 feet long. Like the real thing, it's too big to take in from one spot.

Angkor, in present-day Kampuchea (formerly Cambodia), was founded in the Ninth century. It flourished until the 15th, when its people abandoned it under pressure from foreign enemies. Swallowed by jungle foliage, the city remained unknown to the outside world until a French explorer visited it in the 19th century.

The exhibit grew from a trip to Angkor last fall by a Geographic team headed by editor Wilbur E. Garrett. The package of architectural diagrams, a sound and slide show and paintings of life during the empire's heyday, is a well-crafted introduction to the Khmer civilization.

But it has an important political message too -- that Angkor is endangered by war. Angkor has been a battlefront since the Indochina conflict engulfed Cambodia in 1970. Restoration work has stopped. Statues have been scarred by bullets and looted for sale abroad. Before and after pictures taken by the Geographic team document these sad losses.

The exhibit is sponsored by the U.N. Educational, Scientific and Cultural Organization (UNESCO), which is calling for creation of a neutral zone around Angkor. The political realities of today's Kampuchea -- Angkor is controlled by the pro-Soviet Heng Samrin government, but guerrillas supported by China also operate in the area -- make this solution seem unlikely, though no less desirable.

Many visitors will wonder why the exhibit has no actual samples of Khmer artwork. Editor Garrett said that thought was given to including some, but in the end putting such booty on display didn't seem an appropriate way to argue that the plunder must stop.

ANGKOR WAT -- At the National Geographic through August 29. Open 9 to 5 Saturdays and holidays, 10 to 5 Sundays, 9 to 6 Monday through Friday.