Its capital is also called Lạng Sơn, which is a strategically important town at the border with China and is 137 kilometres (85 mi) northeast of Hanoi connected by rail and road.

[8] It is accessible by road and rail from Hanoi, the Vietnamese capital, and it is the northernmost point on National Route 1.

However, in recent years economic development has received full attention to exploit its rich mineral resources.

Important historical places of interest in the province are the war-ravaged Đồng Đăng border town, which has rich war history and attracts visitors, two large limestone caves within a short distance from the Lạng Sơn town, and a 16th-century citadel of the Ming dynasty.

This period is marked by the trade route that existed between China and India that passed from the Red River Delta through Nanning to Guangzhou.

[7] 7,000–9,000 years ago the limestone caves of the province were inhabited by early settlers of the Bac Son culture.

[8] Later, under the Lý dynasty an extensive market was established at Vĩnh Bình on the Kỳ Cùng River.

[10] Consequently, the Yongle Emperor (of Ming China) launched a punitive expedition against him due to this hostile act.

[10] During the reign of the Ming dynasty, during the period 1527 and 1592, Lạng Sơn was vastly fortified in view of its strategic importance at the border, which is seen even now; a citadel of this dynasty is located to the west of the Lạng Sơn town on a limestone rock outcrop.

[9] In 1922–25 M. Coloni extensively explored Lạng Sơn province and identified 43 sites related to the ancient Bac Son culture in the mountains.

They crossed the Vietnam China border and entered 12 kilometres (7.5 mi) inside, very close to the Lạng Sơn railway station.

[12] After Ho Chi Minh's government was established in September 1945, Japanese had surrendered to the British and Indian Army, under the terms of the Potsdam Conference, to the south of the 16th parallel, while the Chinese Nationalist Party (the Kuomintang).

However, the Viet Minh pursue the French Army, they had a very decisive victory on Highway 4 and they had to finally withdraw from Lạng Sơn.

[7] On June 7, 1949, the district of Lộc Bình was transferred from Hải Ninh province into Lạng Sơn.

The 243 kilometres (151 mi) Kỳ or Kyu River flows through Lạng Sơn town and alluvial plains are formed in the valley that is surrounded by high mountains of about 1,000 metres (3,300 ft) height.

The Bản Thín River, a tributary of the Kỳ Cùng, which is 52 kilometres (32 mi) long with a catchment area of 320 square kilometres (120 sq mi), has its source in a mountainous region in Guangxi in China, and empties into the Kỳ Cùng in the commune of Khuất Xá in Lộc Bình Province.

[19] The most accessed is the Friendship Gate called the Hữu Nghị Quan crossing at Đồng Đăng connecting to Pingxiang town in China.

There is an international train service, an express route, opened in 1996 from Hanoi to Beijing (China), which operates twice a week on Tuesday and Friday that passes through Lạng Sơn Town and Đồng Đăng through this gate which has three-hour stop at the border town to complete formalities of entry from one country to the other.

[14][19] Lạng Sơn is 155 kilometres (96 mi) to the northwest of Hanoi and National Highways 1 and 1 A and passes the Chi Lăng pass (the site of Lê Lợi's victory over 100,000 Ming invaders from China in 1427) and Bắc Giang on National Highway 1A.

Lạng Sơn is subdivided into 11 district-level sub-divisions and 200 commune-level sub-divisions: According to the General Statistics Office of the Government of Vietnam, the population of Lạng Sơn Province, as of 2019, was 781,655[2] with a density of 94 persons per km2 over a total land area of 8,310.09 square kilometres (3,208.54 sq mi).

Apart from the war-ravaged Đồng Đăng Border town, which has a rich war history that attracts many visitors, the other historical places of interest in the province are two large limestone caves located a short distance from Lạng Sơn town, and a 16th-century citadel of the Ming dynasty.

The Tam Thanh Cave is very large with three chambers, a water pond, and has a window opening which provides scenic views of vast rice fields outside.

The Ngoc Tuyen River flows through this cave into the mountain, an unusual feature which is described as "a dramatic sight."

A plaque erected near the cave depicts a French resident of Lạng Sơn in full European dress.

[7][14] The Ming dynasty citadel, a 16th-century monument located in a desolate area on a rock outcrop, is bounded by the east–west facing walls and can be accessed using the Tam Tinh road from Lạng Sơn city.

Northeast Viet Nam has 36% of the country's 1.15 million hectares of rocky mountains out of which Lạng Sơn and Cao Bằng provinces account for a substantial part of limestone formations.