Ban Gioc – Detian Falls are 2 waterfalls on the Quây Son River or Guichun River straddling the Sino-Vietnamese border, located in the Karst hills of Daxin County, Guangxi and in the district of Trung Khanh District, Cao Bằng province on the Vietnamese side, 272 km (169 mi) north of Hanoi. The Detian Falls is situated on the border between China and Vietnam. It is, in fact, the fourth largest cross-border falls in the world after Niagara, Victoria and Iguazu. Due to the various border conflicts between the two countries the area has only recently been opened to tourism. The waterfall drops 30 m (98 ft). It is separated into three falls by rocks and trees, and the thundering effect of the water hitting the cliffs can be heard from afar.