Fort Mosta (Musta) was built on the Victoria Lines between 1875 and 1880 to cover the area around the mouth of Wied il-Ghasel. Fort Mosta was similar in design to other British forts built at this time with a polygonal enceinte. The guns are mounted in a fan shape around a detached keep with its’ casemated barracks and magazines.
To start with the keep was armed with seven 64-pdr SB guns primarily for local defence. Two of these 64-pdr guns were mounted in Haxo Casemates facing out to the north. In 1886 it was proposed to arm the fort with two 6-inch BL gun on disappearing mounts. and these were eventually built and can be seen today.
During World War 2 the Fort was a central defence point and has a number of pillboxes in the vicinity.
Fort Mosta does not appear to have been regarded as a successful fort, primarily because it appears to have been built on clay and prone to ground movement. Fort Mosta had no coastal defence role. The Fort has been used for many years a military magazine.
Fort Mosta was one of the three forts built on the Victoria Lines (North-West Frontier), the other two forts being: