Most of them probably have no idea. The structure has been dismantled, its military geometry softened by time and use, and the site has long since been absorbed into the quiet ritual of outdoor swimming that Dubliners have practised on this wall for generations. That a coastal fortification once commanded this stretch of water is easy to miss entirely.

The battery was built in 1793 by the Board of Ordnance and armed with five 24-pounder guns, heavy artillery pieces capable of hitting ships at considerable range, positioned to control the river channel and the waters around the Poolbeg lighthouse. It was known as the Half Moon Battery, a name likely describing the curved or semicircular form that such defensive works often took, and also as the Five Gun Battery, a straightforward reference to its armament. An addition was made to the structure in 1795. Writing in 1995, the historian Paul Kerrigan placed it within a broader line of coastal defences protecting Dublin Bay, alongside the nearby Pigeon House Fort to the west. Together they guarded the port of Dublin and Sandymount Strand to the south during a period of real anxiety about seaborne threat, particularly in the years surrounding the 1798 rebellion and the broader instability of the Napoleonic era in Europe. The battery's location, some 800 metres east of the Pigeon House along the South Wall, is recorded on John Taylor's 1816 survey map of the Dublin environs. Kerrigan noted that part of the structure survives, though not enough remains to determine with certainty how the guns were arranged.

The South Wall is accessible on foot from the Poolbeg area, following the wall east from the Pigeon House towards the red and white lighthouse at its tip. The walk itself is exposed and best attempted in calm weather; the wall sits low against the water and there is little shelter. The remnant of the battery sits roughly 800 metres short of the lighthouse, though its form is now fragmentary and easy to pass without recognition. What the site does retain is its position, and the view back across the bay from here, with the city behind the Pigeon House chimneys and the water on both sides, gives some sense of why anyone wanting to control the approach to Dublin Harbour would have chosen this particular point.