The Basumtso is the biggest freshwater lake in eastern Tibet. It is located to the northeast of Gongbo-gyamda County and is about 40 kilometers away from the main road of the No. 318 National highway. The lake is shaped like a crescent. It's also located at an elevation of over 3400 meters, with an average depth of more than 60 meters.

In the middle of the lake, there is an island with a monastery built in the last years of Tang Dynasty. The monastery belongs to the Ningmapa sect, which has a history of more than 600 years. The construction of the monastery was lead by the famous Ningmapa monk Sangye Lingpa. Indian Guru Padmasambhava is worshiped at the monastery.