The wall itself was begun in 1748 to hold back the sands of the South Bull and protect the harbour channel, and by the time it was complete it had become something more than a sea defence. Midway along it, the authorities had created a garrison capable of holding the city itself against threat from sea or from within.

The Pigeon House Fort was established as a military post shortly before the 1798 Rising, intended, as historian Paul Kerrigan noted, to serve as a citadel and refuge for the Dublin administration and garrison, an isolated strong-point with its own harbour. A blockhouse had existed on the site since 1760, used for storing tools and salvaged cargo, but the military transformation was altogether more serious in scale. By June 1804 the fort held thirty-five artillerymen and sixty soldiers, along with a bombproof shelter, a vaulted structure capable of accommodating 200 men in an emergency, and an arsenal that included seven 24-pounder guns, three 12-pounders, an 18-pounder, howitzers, and eight mortars. A 900-foot-by-450-foot harbour basin sat adjacent, originally built for mail packet ships, though it fell into disuse once the harbours at Howth and Dún Laoghaire were completed. A Royal Engineers report of November 1805 proposed expanding the fort to more than six times its size, with demi-bastions, a ravelin, and extensive new construction over the strand; the plan was never carried out. Weston St John Joyce, writing in 1921, put the eventual cost of works at over £100,000.

Access to the site today is via the South Wall road from Ringsend, the same approach that was once guarded by a drawbridge and an armoury. Parts of the perimeter wall and rampart on the west and south still survive, along with arched gun embrasures, openings in the wall through which cannon were trained, and a bow-fronted house at the south-east angle that appears on plans dating to 1805. Extensive land reclamation means the sea no longer reaches the walls at high tide as it once did, and a large power station now occupies the eastern portion of the site, replacing most of the military structures. What remains is fragmentary but legible, and the walk along the South Wall to reach it, with the bay opening out on both sides, gives some sense of just how exposed and deliberate a position this once was.