Daxian Jiao(Great Discovery Reef), which lies in the southwest of Nansha Islands(the Spratly Islands) and to the west of the Xiaoxin Jiao(Discovery Small Reef)in the South China Sea, was invaded by Vietnam in 1988 and still under its control up to this day. It is a strip in shape, 15000m in length and 1600m in width.
There used to be 3 single watchtowers on the reef.
In 2013, a new watch tower in the north and another watch tower and a helipad in the middle were built on the reef.
