Detian Falls, called Bản Giốc Falls in Vietnam, is a waterfall on the Quây Sơn River (the Guichun River in Chinese) where it crosses the border between Daxin County in China’s Guangxi Zhuang Autonomous Region and Cao Bằng Province in Vietnam, about 272 km (169 mi) north of Hanoi. In the rainy season its two main falls merge into a single front about 208 m wide, which makes it the fourth-largest waterfall on an international border after Iguazu, Victoria and Niagara. Sources disagree on its height: the English Wikipedia article gives a drop of about 30 m, while Chinese sources put the main fall at 60 to 70 m. The border runs through the middle of the main fall, so two countries, several ethnic groups and two tourist industries share one river.
Detian is not a wilderness waterfall. It sits in karst valleys farmed by Tày, Nùng and Zhuang families, on a border that was a war front in 1979 and now lets tour groups cross by appointment. This guide looks at the falls through the people who live beside them.
Đàm Thủy and Detian Village: Two Communities at One Waterfall
On the Vietnamese side the falls lie in Đàm Thủy commune, about 80 km northeast of the provincial seat of Cao Bằng. Until July 2025 Đàm Thủy belonged to Trùng Khánh district, a rural district of 688 km² with 70,424 people in 2020. That year Vietnam abolished its district level of government altogether, and Đàm Thủy now reports directly to the province, one of 56 commune-level units in Cao Bằng. On the Chinese side the falls belong to Detian village in Shuolong town, Daxin County, which is administered by the prefecture-level city of Chongzuo. Nanning, the capital of Guangxi, is about 208 km away.
The river itself explains why the two communities sit so close. The Quây Sơn rises in Jingxi County in China, enters Vietnam at Pò Peo in Đình Phong commune and loops around the foot of Cô Muông mountain. It then crosses the fields of Đàm Thủy and the maize plots above Bản Giốc hamlet before it returns to the border and splits into several channels. There the bed drops suddenly and the river falls. A wooded island in the middle divides the water into three streams, and below the falls the river turns into Chinese territory.
The landscape both communities farm is mature karst. The falls run over layers of Middle Devonian dolomitic limestone, and over thousands of years the river has worn back its crest and moved slowly upstream. Most of the year it now looks like two separate falls, which only join into one in the summer rains. Many small streams spring from fissures along the lower levels of the valley. Around the falls the karst holds other attractions too: the Ngườm Ngao cave, about 5 km from the falls on the Vietnamese side, runs for about 3 km, and the Tongling Gorge in Baise, reachable only through a cavern, has plants found nowhere else.
Tày, Nùng and Zhuang: The Peoples of the Quây Sơn Valley
The people on both banks are closely related. The Zhuang of Guangxi and the Tày and Nùng of northern Vietnam all speak Northern Tai languages and are sometimes grouped together as the Rau or Rao people. With an estimated 19 million people, the Zhuang are the largest ethnic minority in China, and Chongzuo, the city that runs Daxin County, is one of their heartlands: about 88 percent of its people are Zhuang. The Hua Mountain rock paintings on the Ming River in Chongzuo, made 1,800 to 2,500 years ago, are among the largest groups of pictographs in the world and an early record of Zhuang culture.
Across the river, Cao Bằng Province covers 6,700 km² and had 547,849 people in 2023. The Tày make up about 41 percent of the population and the Nùng nearly 30 percent, while the Kinh, Vietnam’s majority group, are just over 5 percent.
One historical figure belongs to both traditions. Nùng Trí Cao was an 11th-century Tày-Nùng leader from this frontier who rebelled against the Vietnamese Lý dynasty, and the area became part of Đại Việt in 1039 when Emperor Lý Thái Tông drove him out. He went on to declare a kingdom of his own. Today a shrine to him stands at the Bản Giốc pagoda beside the falls, and one of Cao Bằng’s three wards is named after him. The province’s mountains have hidden other rebels since: Hồ Chí Minh returned from China on 28 January 1941 and set up his headquarters in a cave at Pác Bó, north of the provincial capital.
Chestnuts, Longans and Manganese: Making a Living Around the Falls
Before tourism, the valley lived from farming, and it still does. Trùng Khánh is known across Vietnam for its Chinese chestnuts, called mác lịch in Tày; a 1999 analysis by Vietnam’s Fruit and Vegetable Research Institute found they contain 3.12 to 3.62 percent protein and 43 to 46 percent carbohydrate. The fields and maize plots that frame photographs of the falls are working farmland, not scenery kept for visitors.
On the Chinese side, Daxin County covers 2,756 km² and is known for longan. It also produces Wancheng kuding tea, a bitter tea from Kuding village that holds Chinese geographical-indication status. The county’s biggest industry lies underground: the Xialei manganese mine is the only manganese deposit in China with reserves above 100 million tonnes, and neighbouring Trùng Khánh, across the border, also produces manganese. Across Chongzuo as a whole, sugarcane is the centre of farming, alongside rice, cassava, cinnamon and fruit.
Farming has not held the population steady. Daxin’s resident population fell from 296,555 in the 2010 census to 282,563 in 2020, a drop of 4.72 percent in ten years. Chongzuo as a whole had about 2.05 million residents at the end of 2024.
The river also produces electricity. About 4.5 km upstream of the falls, the Bản Rạ hydropower station, finished in April 2012, has three turbines with a combined 18 MW. It takes water out of the river at Bản Rạ and returns it at Bản Gun, leaving about 3 km of the channel close to dry. Chinese sources describe December to May as the low-water season, when more rock shows around the falls.
From Marker 53 to the 1999 Treaty: How the Border Shaped Local Life
Families on both banks have lived with an uncertain boundary for more than a century. France and Qing China fixed the line in conventions of 1887 and 1895, and a demarcation record of 31 May 1892 says the border follows the middle of the river up to the falls. A stone marker on the road above the falls, inscribed in French and Chinese, is marker 53 of that survey. The documents did not describe the ground above the crest, where two channels wrap around the islet of Pò Thoong, and both countries claimed it.
The frontier became a war front in the Sino-Vietnamese War of February and March 1979, when Chinese troops crossed into northern Vietnam from Chongzuo. Relations between the two countries were not normalised until November 1991. Some Vietnamese commentators still argue that the whole falls belonged to Vietnam and that the marker was moved during or after the war, a claim Vietnam’s deputy foreign minister Vũ Dũng called baseless. The land border, 1,297 km long in total, was settled by the treaty of 30 December 1999. Under the agreement both sides reached in 2008, the line runs from marker 53 across Pò Thoong to the centre of the main fall. Vietnam holds half of the main fall, all of the secondary fall and about a quarter of the islet.
Tour Rafts, a Pagoda and the 2023 Cross-Border Tourism Zone
Once the line was fixed, both sides began to build a tourist economy on it. In November 2015 China and Vietnam signed an agreement to set up and jointly develop the falls as a scenic area. On the Chinese side, the Detian cross-border waterfall scenic area was upgraded to national 5A status, China’s highest rating, in 2018. A year later a subsidiary of China Tourism Group became the main investor, and on 28 May 2019 it set up an operating company for a project expected to cost about 1.45 billion yuan. Television crews have used the falls as a location, among them the drama Hua Qiangu.
The two sides have not grown at the same pace. According to figures from Cao Bằng’s culture, sports and tourism department, the Vietnamese side has received about 30,000 visitors a year while the Chinese side has received nearly a million. On the Vietnamese bank, the Phật Tích Trúc Lâm Bản Giốc pagoda was begun in June 2013 on Phia Nhằm hill, 500 m from the falls, on a 2-hectare site that cost about 38 billion đồng, mostly raised from donations. It was the first pagoda that Cao Bằng’s authorities approved on this stretch of the northern frontier.
The next step came on 15 September 2023, when the Detian (Bản Giốc) Falls Cross-Border Tourism Cooperation Zone began trial operation. It was China’s first zone of its kind. Visitors cross only in booked, size-limited groups, follow fixed routes and may spend at most five hours on the other side. Chinese sources recommend July to November, when the rains raise the river, the water runs clear and the falls merge into one front.
For the falls that rank above Detian along international borders, see our list of the widest waterfalls in the world. How limestone dissolves into towers and caves like those around Đàm Thủy is explained in what karst topography is, and the wider northern mountains are covered in our guide to Vietnam’s geography.