The site comprises 20 km of the upper Lar valley in the high Alborz Mountains, from 2,450 m to peaks at 4,540 m. It lies above the Lar Dam, c.10-30 km upstream from the small town of Polur and c.40 km north-east of Tehran. The Lar is in the Caspian watershed, but at this point lies in a rain shadow and the area is relatively arid. For much of its length, the river meanders across a broad, flat-bottomed valley c.500-1,000 m wide. Habitats include a fast-flowing river with extensive shingle banks, patches of dense riverine Salix and Tamarix scrub (with a few trees up to 7-8 m high), small areas of natural wet meadow, open hillsides with steppic vegetation, a number of small, spring-fed alpine meadows in side valleys, and the high crags and summits of neighbouring peaks. There is grazing by sheep, goats and horses. The area was a regular bird-ringing site of the Department of the Environment's Ornithology Unit in the 1970s.