The lake and its surrounds is considered an area of ecological and cultural importance. It is immense: more than 23,000 hectares, 80 kilometres long, up to 10 kilometres wide and 42 metres down at its deepest point. The landscape is stunning, with 1,331 islands, mostly covered in forest, and still, clear water. The region is home to a number of ethnic minority groups, most notably the Dao but also Tay, Nung, Thai, Muong, Giay and others, with many living along the banks of the lake and earning a living from its waters. The area also has historical significance: in 1285 the Thu Vat Battle took place against Mongolian invaders and during the Vietnam/American war Thuy Tien cave was the base of Yen Bai provincial committee.