Ba Be Lake is Vietnam's largest natural freshwater lake — a single continuous body of water 8 km long and up to 800 m wide, despite the name meaning "three lakes." At 178 m above sea level, it sits in a basin ringed by limestone karst peaks rising above 1,000 m. The water is calm, the colour of green glass, and reflects the forest-covered cliffs on clear mornings.
The lake is navigable by wooden motorboat for its full length. Most visitors do a loop that takes the better part of a day, stopping at Puong Cave and the Dau Dang Waterfall at the southern end. The lakeshore Tay villages — Pac Ngoi is the largest — are the main places to overnight; homestays here put you on the water at the right hours.
The lake supports a number of endemic freshwater fish species and is an important water source for the surrounding communities. Swimming is possible from the homestay jetties, though the main draw is the scenery above rather than the water itself.