Situated about 185 km (115 mi) from Vũng Tàu and 230 km (143 mi) from Saigon, the group includes 16 mountainous islands and islets. The total land area reaches 75.15 km2 (29.02 sq mi) and the local population is about 5,000.
The islands are composed of magmatic rocks of different ages. Hon Bay Canh, Hon Cau, Hon Bong Lang composed of Cretaceous microgranit rocks. The Northern part of Con Dao Island composed of quartz diorite and granite - granodiorit of late Mesozoic- early Cenozoic age, and is partially covered by Quaternary marine sediments. The Southern part of this island and Hon Ba island are composed of the riolit and intrusive formations of unknown age. On the western slope of Con Dao Island, there exist of outcrops of diorite and microgranit penetrated by big quartz bands .
On June 16, 1702, the English East India Company founded a settlement on Pulo Condore as an entrepôt for ships plying between India and China. Three years later, on 2 March 1705, the Vietnamese murdered the English agents, destroyed the factory, and expelled the remaining settlers.
During the internecine wars for the Court of Hue, the Nguyen Prince Nguyễn Phúc Ánh ceded the islands to France in the Treaty of Versailles (1787) in return for military assistance. The treaty however was abrogated as France failed to provide the aid.
It was only under conquest that the islands came under French control in 1861. During the French colonial era, the island was made infamous for its penal facilities and the notorious "tiger cages". Vietnamese and Cambodian nationalists were sent here to serve their sentence for anti-French activities. Many Vietnamese Communist leaders were "schooled" on Côn Đảo Island as well.
Many of the islands were given protected status in 1984 as part of Côn Đảo National Park. This natural preserve was subsequently enlarged in 1998. Endangered species protected within the park include the hawksbill turtle, the green turtle, dolphins, and the dugong. Ecosystems represented in the park include seagrass meadow, mangrove and coral reefs.
Côn Đảo National Park is working with the World Wildlife Fund (WWF) Vietnam to further protection in the marine areas, with programs to establish a Marine Protected Area that protects coral reefs, seagrass beds and species, while also developing sustainable nature-based ecotourism. The island's management is strongly geared towards sustainable use, hoping to learn from previous experiences in Vietnam and the region to balance development with conservation.
Côn Sơn Islands include 16 islands, with a total area of 76 km².
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