What once spread across a roughly polygonal footprint, measuring approximately 380 metres west-north-west to east-south-east and up to 320 metres at its widest, is now covered almost entirely by streets and houses built around 1965. The site is marked on the 1837 Ordnance Survey six-inch map simply as "Ordnance Ground", and the label has survived even as the thing it described has not.

The complex was constructed by the British Army around 1800, at a moment when a French landing in Ireland was considered a genuine possibility. Athlone's position on the River Shannon, one of the principal inland routes through the country, made it a strategically obvious place to fortify. The installation comprised an irregular rampart connecting six batteries positioned at the north, west, south-west corner, along the south side, and at the south-east corner, with triangular-shaped guard houses at several of them. Internal pathways linked the batteries across the interior. A battery, a raised platform designed to mount artillery, was the key functional unit of such a defensive system, and here they were arranged to cover approaches from multiple directions, with the elevated site and proximity to the Athlone Canal to the east adding further tactical advantage. Oblique aerial photographs taken in September 1963 still show the earthwork and stone ramparts standing clearly, less than two years before construction of the housing estate began to overwrite them.

Nothing of the fortification is visible at ground level today, and the site gives no outward sign of what it once contained. The Ranelagh battery, a related artillery position, survives approximately 500 metres to the north-north-east, and represents the nearest remaining trace of what was once a more substantial defensive network around the town.