Cầu River (Vietnamese: Sông Cầu) is a river of northern Vietnam. It flows through the provinces/cities of Bắc Kạn, Thái Nguyên, Bắc Giang, Hanoi, Bắc Ninh. It begins at the Phia Bioóc Peak in Chợ Đồn District, west of mountainous province of Bắc Kạn.
The river has a length of 288 km and basin area of 6,030 km².
The Tày people, also known as the Thổ, T'o, Tai Tho, Ngan, Phen, Thu Lao, or Pa Di, is a Central Tai-speaking ethnic group who live in northern Vietnam. According to a 2019 census, there are 1.8 million Tày people living in Vietnam. This makes them the second largest ethnic group in Vietnam after the majority Kinh (Vietnamese) ethnic group. Most live in northern Vietnam in the Cao Bằng, Lạng Sơn, Bắc Kạn, Thái Nguyên, and Quảng Ninh provinces, along the valleys and the lower slopes of the mountains. They also live in some regions of the Bắc Ninh and Bắc Giang provinces. They inhabit fertile plains and are generally agriculturalists, mainly cultivating rice. They also cultivate maize, and sweet potato among other things.
Cao Bằng is a province of the Northeast region of Vietnam. The province has borders with Hà Giang, Tuyên Quang, Bắc Kạn, and Lạng Sơn provinces within Vietnam. It also has a common international border with Guangxi province in China. The province covers 6,700.39 km (2,587.04 mi) and, as of 2023, its population was 547,849 people.
The area has a rich history tracing to the Bronze Age Tây Âu (西甌) Kingdom of the ethnic Tày. Cao Bằng has several points of historical interest as well as many natural features such as the Pác Bó (at the mouth of the confluence of two rivers, the Bằng Giang and Hien rivers) where Hồ Chí Minh in January 1941 established a revolutionary force at Cốc Bó cave, the Mạc emperor's Temple, the Kỳ Sầm Temple, Coi Bin Church, the Bản Giốc waterfall area at the international border between Vietnam and China, and the Thang Hen Mountain Lake.