It covers about 31 sq km and extends from 15th Mile police check post up to and along the edges bordering Rong Chu and Tsomgo Lake. The sanctuary is rich in rare and endangered ground orchids and rhododendrons. Rhododendron nevium, the state tree of Sikkim and Cypripedium tibeticum, the ground slipper orchid on the verge of extinction, are introduced here.

The best season to visit is April-August and October-November.