ARCHITECT John Russell Pope created such a gorgeous setting when he designed Meridian House that anything placed on exhibit there has a tough act to follow.

But it's no problem for "Dancing Faces," the current show of ancient and modern Mexican dance masks. The variety of the masks is astonishing; all are distinctive, even those made of the same materials in the same village at the same time.

Masks have been central to Mexican culture for thousands of years; the exhibit uses photos and mannequins to explain the contexts in which different designs are used in various areas. The Spanish conquerors of Mexico long tried to stamp out the use of masks, which they regarded as heathen, evil and subversive. The modern turistas may succeed where the friars failed: They're buying up masks -- including unauthentic and shoddy examples mass-produced to meet the demand -- at such a rate that traditional designs and methods are disappearing.

Most of this collection was assembled by Victor Jose Moya Rubio, a Mexican engineer who has spent a lifetime seeking outstanding examples, some of which he bought from their owners right in the middle of street festivals.

DANCING FACES -- Through April 15 at Meridian House, 1630 Crescent Place NW (off 16th Street, opposite Meridian Hill Park). Open 1 to 4 Sundays and weekdays. Guided tours on request. 667-6800.