Tsomgo or popularly called Changu Lake is one of the most popular tourist sites in Sikkim it literally means the "source of the lake" in Bhutia language. Just about 38 km away from Gangtok, this serene lake is situated at an altitude of 12,000 ft on the Gangtok Nathu La highway. It falls in the restricted area and hence an inner line permit is required by tourists to visit this place. Foreign nationals require special permits to visit this lake. The lake is about 1 km. Long, oval in shape, 15 meters deep and is considered sacred by the local people. It's cool, placid water harmonizes with the scenic beauty around. A small temple of lord Siva is constructed on the lakeside. This placid lake remains frozen during the winter months. The local people operate tea shops and places to eat and also keep snow boots and warm clothing for hire and rental.
Between May and July the semi alpine to alpine landscape offers a variety of flowers including primulas, gentians, poppies, irises and rhododendrons. The Kyongnosla Alpine Sanctuary in the vicinity of the lake is also famous for its flora and fauna. Rare, endangered ground orchids and rhododendrons interspersed among tall junipers and taller silver firs are among the important plants present.