Cam Son Lake

A sheet of water so wide that a person standing on one shore cannot see the other.

This is Cấm Sơn Lake, one of the largest freshwater lakes in the northeastern region of Vietnam, now part of Bắc Ninh province. Many older documents list it under Lục Ngạn, Bắc Giang. Place names can change, but the water stays as it was: green, wide and calm.

The lake's story begins in February 1966. The country was at war and life was hard, yet people still decided to build a large irrigation project. They dammed the Cấm Sơn waters coming down from Hữu Lũng in Lạng Sơn, and the water gathered into a lake. Three and a half years later, in July 1969, the work was finished. Its first purpose was not tourism but watering fields. Thousands of hectares of farmland in the former Bắc Giang area and in Lạng Sơn are watered by it. Today the lake has another job, more important, that many visitors do not know about. It supplies household water to more than 32,000 families downstream.

So a visitor in a boat, looking at the green surface, is floating on a source that tens of thousands of families use every day for cooking and daily needs.

Provincial sources give the size. In a normal season the water covers about 2,500 to 2,600 hectares, and in the rainy season it can reach about 3,000. The lake is almost 30 kilometers long. It is 7 kilometers wide at its widest and 200 meters at its narrowest. Many islands rise from the water, and mountains and forest surround it all.

Crossing the lake by boat is a quiet thing in itself. The mountains lean in from both sides, their shadows lie on the water, and the only sounds are the boat engine and birds far away. A report from Sơn Hải commune in early 2026 says the lake has more than 10 boats for visitors, and that in the first quarter alone the lake received about 1,600 visits.

People live around the lake too. The residents are Nùng, Tày and Kinh. The Tày and the Nùng are two peoples of northern Vietnam with closely related languages and similar cultures. The Kinh are the majority ethnic group of Vietnam. For many villages, the main way to get around is by boat.

A community tourism plan of the former Bắc Giang province mentions Bắc Hoa village in Tân Sơn commune, now part of this area. It is linked with the An Phú cooperative and with the nhà trình tường of the Nùng people. These houses are built of thick packed earth, with upright walls that stay cool in summer and warm in winter. It is a kind of architecture tied to mountain and soil, unlike any house in a city.

People also speak often of the lake's specialties: lake shrimp, lake fish known as cá hồ một nắng, or "one sun", hill chicken and wild bamboo shoots. These belong to the lake and the forest. They are not food that could simply be brought in from somewhere else.

Writers and musicians have mentioned Cấm Sơn in many pages and songs. Local people say that the song "Hồ trên núi," or "Lake on the Mountain," by the composer Phó Đức Phương was inspired by a scene like this one. With that song in mind, or looking at the water early in the morning, one can see why people call it a lake on the mountain, though it really lies in a valley. From a boat in the middle, with mountains on all four sides, it feels like a patch of sky of its own, apart from the noisy life outside.