Green Hill Fort on Thursday Island was built between 1891 to 1893 as part of Australia's defence against a possible Russian invasion. It was eventually decommissioned some time in 1927 and the buildings were demolished and the guns were spiked. Green Hill is a small grassy hill about 58 metres above sea level at the western end of Thursday Island.
There are five rooms with 600 millimetre thick concrete walls used for ammunition storage. The initial buildings on site were the general storeroom, shell store, cordite room, lamp room and artillery store. A timber and corrugated iron guardhouse (25 inch by 15 inch) was also built over a 20000 gallon underground well. A cooling plant machine room and a powder room were added in 1912. Air conditioning ducts were installed from the cooling plant machine room to the cordite store.