Glen Echo is the perfect spot for a dance festival: Its eclectic nooks and crannies, along with the revamped Spanish Ballroom, provide performers with spaces both informal and formal in which to unfurl their work. This Sunday, Glen Echo Dance Theater, together with the National Park Service, the state of Maryland and the Montgomery County Arts Councils, sponsors an Improvisation Festival. Beginning at 11 with a workshop by dancer/orator Mary-Averette Seelye, the event continues throughout the afternoon, featuring a number of the area's more adventurous dance-makers.

Outdoors in the open space near Yurt Village you might see several performers, collectively known as Talus, clambering, rolling and bouncing off each other's backs; it's called contact improvisation. The spontaneous movement and the daring and trust involved make for a novel viewing experience. Later on in that same space, Beth Burkhardt, a dancer known for her careful improvisations with musicians, presents her definition of improvisation.

Inside the Spanish Ballroom, two companies perform back to back. Sally Nash and the Last Minute Wood Company, who hail from Rappahanock County, will present two works, one of them a premiere, based on material that Nash has culled from dreams, childhood reminiscences and group interaction and improvisation. Later, Duets Etc..., a new, very small troupe whose mainstays are Helen Rea and Don Zuckerman, will show how diverse choreographers explore the duet form. IMPROVISATION FESTIVAL -- Sunday beginning at 11, with last performance scheduled to start at 2:45, at Glen Echo Park. Intersection of MacArthur Boulevard and Goldsboro Road. Performances in Spanish Ballroom are $2 for adults; all other events free. Call 229-6022.