The Bankstown bunker is a three-story building that was mostly underground. It was secretly used during the Second World War by the Australian air force. Builders started to build the bunker in 1942. Workers and volunteers began to work inside the bunker in January 1945. It was called the Sydney "Air Defence Headquarters" and replaced another secret air force base that was in a secret tunnel. This was the Number One Fighter Sector Headquarters underneath St. James train station in Sydney. After that, it was moved to a picture theatre in Bankstown called the Capital Hall. The main job for the people who worked in the bunker, was to track all planes in the eastern area of the South West Pacific. Some of the people who worked in the bunker were from the No.2 Volunteer Air Observer Corps (VOAC), The Women's Auxiliary Australian Air Force and a few members of the Royal Australian Air Force and the United States Army Air Forces. Workers worked in the bunker 24 hours a day seven days a week in shifts called "Flights". The people who worked inside the bunker traveled to work in buses with tinted windows. Everyone that worked in the bunker had to receive special training.