The Batterie du Lazaret is built on the tip of a headland overlooking the entrance to Diego Suarez Bay. The original battery was built in 1898 to mount four 138 mm Model 1870 guns. The guns are each mounted in separate pits with traverses. The traverses are used as crew shelter and expense magazines. The layout of the battery is very similar to La Batterie de l’ Hopital. A Defence Electric Light was installed to the front of the battery.
To the rear of the original battery a new 90 mm Anti-Aircraft gun battery was built in 1939 with two emplacements. The 90 mm battery is largely underground with a tramway linking the various parts of the battery. This anti-aircraft battery is credit with shooting down some allied aircraft during Operation Ironclad in 1942 before Hurricane fighter bombers neutralised the French Battery.