It is the only one of its kind in the world that was established to promote research on the language and traditions of Tibet as well as into Mahayana Buddhism. Just beside this institute there is an orchid sanctuary which houses most of the 454 species of orchid found in Sikkim, depending on the season. The Institute houses a library of more than 30,000 books on Buddhism, astrology, medicine, philosophy and rare Thankas (Tibetan religious paintings on cloth). About a Km beyond the institute stands a huge chorten whose gold apex is visible from many points in Gangtok. The institute promotes a serious study of Buddhist philosophy and religion and is a leading authority on the subject. The most prestigious of its kind in India - this Buddhist Institute is a treasure trove of vast collection of rare Lepcha, Tibetan and Sanskrit manuscripts, statues and rare Thankas and has over 200 Buddhist icons. There is another orchid sanctuary called the Orchidarium located along side the Rani Khola, a tributary of the Teesta River. On the top of the Ridge there is a Flower Exhibition Centre featuring orchids, seasonal flowers and bonsai, which is open from April to June and September until late November. The best times to visit the sanctuary are March to early May and the end of September to the beginning of December.