The freshwater Lake Ba Be is the only significant natural upland lake in the North of Viet Nam. It was formed by combined tectonic force and severe erosion in karst area. Surrounding limestone hills rise to 500 - 600 above sea level. There are a number of caves in this limestone area: the most famous is Puong Grotto through which the Nang River flows.

The lake consists of three parts, Pe leng, Pe lu and Pe lam; hence the name Ba (three) Be (sea). It measures 9 km in total length, with the width between 0.2 km and 1.7 km. The average depth varies from 17 m to 23 m, the maximum depth reaching 29 m. Ba Be is connected with the Nang River by Be Cam Channel, to which the lake water drains during the dry season. The lake thus serves as a natural reservoir for the Nang River system, while Dau Dang Waterfall plays a role of natural dam for the lake.

The beautiful and magnificent scenery of Ba Be and its surroundings has considerable potential for both national and international tourism. The lake and forests around it are designated as a protected area by the government. The lake is also important for the life of the local people belonging to an ethnic minority group Tay (total population 1,283 in 184 families in 1990) as the source of water, navigation and transportation routes, and fishing ground (Q).