This reserve covers a part of Jengging, Tuting, Gelling and Singa in Upper Siang district and Mippi and Anini in Dibang Valley district. It covers an area of 5111.5 sq km with altitudinal variation from 500 to 16000 ft height that leads to snow clad peaks and glacial lakes. The reserve accommodates eight types of forests namely- sub-tropical broad leaved, sub-tropical pine, temperate broad leaved, temperate conifer, sub-alpine scrubs, alpine pastures, bamboo groves and grasslands. It is one of the identified bio-diversity hot spots in the country.

The Gelling-Tuting-Singa triangle constitutes the ‘Pemako Zone’ of the Tibetan form of Buddhism with small hamlets of the lamas amidst serene natural environment. The Gompas and Buddhist shrines have golden Buddha statues, old scrolls and other traditional artifacts of the Tibetan form of Buddhism.