With an area of 1.2 km², Tai A Chau is the largest of the Soko Islands. It is located 4.5 km to the south of Lantau Island and about 2 km north of the boundary of the Hong Kong territorial waters. The island has small hills with heights ranging from 85m to 154m. Its coastline is mainly steeply sloped and rocky in nature.
There were historically two villages on the island: Ha Tsuen and Sheung Tsuen on the west and south sides of the island. The villagers left in the 1980s, when a detention camp for Vietnamese refugees was built. In 1937, Walter Schofield, then a Cadet Officer in the Hong Kong Civil Service, wrote "There is a shrimp paste factory here which exports to Europe and America". Tai A Chau Detention Centre was home to thousands of Vietnamese refugees from 1991 to 1996. The centre was closed prior to the handover in 1997 and all the building structures were demolished.