Lower Union Gallery
Lower Union Gallery was built during the Great Siege in 1789 and lies above the King’s and Queen’s Lines. It is a rock cut chamber with four gun emplacements. The Battery stands immediately above the Retrenchment Wall which runs down to the Prince’s Lines.
In 1859 the battery mounted three 24-pdr guns, but by 1886 this was reduced to a single 64/32lbs RML gun. All four embrasures have mantle rails on them, so it is assumed that all four embrasures were used at one time or another.
The tunnel gives access to another gate leading into the tunnels of the Upper Union Gallery and then up to Willis Plateau.