Ban Gioc – Detian Falls are 2 waterfalls on the Quay Sơn River or Guichun River straddling the Sino-Vietnamese border, located in the Karst hills of Daxin County in the Chongzuo prefecture-level city of Guangxi Province, on the Chinese side, and in the district of Trung Khanh District, Cao Bang province on the Vietnamese side, 272 km north of Hanoi.
The waterfall drops thirty meters. 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.
It is currently the 4th largest waterfall along a national border, after Iguazu Falls, Victoria Falls, and Niagara Falls and was one of the crossing points for China’s army during the brief Sino-Vietnamese War. Nearby there is the Tongling Gorge accessible only through a cavern from an adjoining gorge. Rediscovered only recently, it has many species of endemic plants, found only in the gorge, and in the past was used as a hideout by local bandits, whose treasure is occasionally still found in the cliff-side caves.
A road running along the top of the falls leads to a stone marker that demarcates the border between China and Vietnam in French and Chinese. Modern disputes arose as there are discrepancies as to the correlating legal documents on border demarcation and the placement of markers between the French and Qing administrations in the 19th century.