Nanzi Island (Southwest Cay), which lies in the south of Shuangzi Reef (North Danger Reef) of Nansha Islands (Spratly Islands) in the South China Sea, was first occupied by Philippine in 1971, and later captured by South Vietnam in 1975. After the reunification of Vietnam in 1975, it has been a Vietnamese-occupied island up to today. As one of the main islands of Shuangzi Reef (North Danger Reef), it is oval in shape, about 650m in length, 500m in width, and lies from the northeast to southwest.
In 2014, Vietnam started land reclamation and harbor basin construction, which has totaled an area of 0.03km2.
By 2016, there had been over 20 buildings of various kinds, including a radar antenna, a helipad, terminal, a soccer field, breakwater and lighthouse.
Since 2018, there wasn’t facility newly built. Only Vegetaiton have cover the southern part of the island.
From 2018 to 2020, two radar stations were built in the north of the island, next to which is the suspected missile launch site.
