Châu Đốc sits on the Hậu, the western branch of the Mekong that leaves Cambodia and becomes Vietnamese a few kilometres upstream, about 250 kilometres west of Ho Chi Minh City. This was Khmer land until 1757, when the Cambodian king ceded it to the Nguyễn Lords, and for the next century it was a frontier in the fullest sense - fortified, fought over, repeatedly changing hands. Gia Long built a fort here in 1815. Minh Mạng raised it to a garrison in 1825 and threw up a new eight-sided citadel in 1831, and in 1832 made it the seat of the newly created An Giang province. The other great work of that era leaves town heading southwest in a line so straight it looks drawn with a ruler: the Vĩnh Tế Canal, cut by hand toward Hà Tiên, and the reason a fishing settlement became a strategic place worth arguing about.

Núi Sam rises 284 metres out of ground that is otherwise flat to the horizon in every direction, which in the delta is enough to make a mountain sacred. The temple of Bà Chúa Xứ, the Holy Mother of the Realm, stands at its foot in Vĩnh Tế village, and she is a working goddess: petitioned for business, for health, for protection along a border that has rarely been quiet. The legend of how she came down the hill is better than any official history. Forty of the village's strongest men tried to carry her and could not shift her; nine young women lifted her without difficulty and brought her to the spot where she chose to stay. Her festival runs from the twenty-third to the twenty-seventh of the fourth lunar month, usually falling in May, and it fills the town.

Cholera swept the delta in 1849, and out of the epidemic came a healer named Đoàn Minh Huyên, who moved among the dying around Châu Đốc and the Seven Mountains and was taken by those he saved for a living Buddha sent to rescue the world. His followers wore amulets reading Bửu Sơn Kỳ Hương - the Strange Fragrance from the Precious Mountain - and the tradition he founded became one of the most persistent religious currents in the south. Huyên died in 1856. Nearly a century later Huỳnh Phú Sổ carried the same millenarian teaching forward as Hòa Hảo, a faith with millions of adherents in the delta that still venerates both men. It is not a coincidence that this happened here. Frontier country, plague, a horizon of low sacred mountains and a border that keeps moving: the delta's prophets have always come from its edges.

Cross the Hậu by ferry to Châu Giang and the call to prayer replaces the temple gong. The Cham of An Giang are Sunni Muslims of the Shafi'i school - Ramadan, Eid, minarets among the sugar palms - and they form the core of a Muslim world that spans the border into Cambodia. Vietnam's 2019 census counted just under 179,000 Cham nationwide, and the delta communities are known for their weaving and for tung lamaow, the beef sausage that is an An Giang speciality. In the same few kilometres you can find Khmer Theravada wats with their steep tiled roofs, Vietnamese Mahayana pagodas thick with incense, and the mosque at Đa Phước. Three liturgical calendars, three languages, one market.

The market that sprawls through the middle of town, covered along Bạch Đằng street, is above all a market for mắm - fermented fish, mounded in basins by species and cure, the smell arriving several stalls before you do. Anchovy fish sauce and basa catfish are what Châu Đốc sells; the catfish are raised in pens in the river, and whole households live on the water above their own stock. Travellers mostly know the town as a doorway. One ferry company still runs the speedboat up to Phnom Penh - about four hours on the water and two more standing at the border post - and most visitors give Châu Đốc a single night before crossing. Since June 2025 the town is not even a city on paper: the merger of Kiên Giang into An Giang province swept away the old district tier, and Châu Đốc, a provincial seat on and off since 1832, is now a ward. The mắm sellers have seen this sort of thing before.