What survives is almost nothing, yet the site sits at the centre of some of the most consequential military engineering ever carried out on Irish soil. The fort in question is the one known in the seventeenth century as Ireton's Fort, a bastioned fort, meaning an earthwork strongpoint with projecting angular corners designed to eliminate blind spots in defensive fire, and it was the largest of four such works constructed by Parliamentary forces during the siege of Limerick in 1651.

In May of that year, Lieutenant-General Henry Ireton marched on Limerick with an army of 8,000. After being repulsed from the northern, Clare bank of the Shannon, he shifted the bulk of his forces south of the city and, by late June, his engineers had begun throwing up an arc of ditches, earthen ramparts, and forts designed to encircle Irish Town, the southern section of the city. Ireton's Fort anchored the northern end of this arc, garrisoned alongside Cromwell's Fort to its south by a combined force of 800 soldiers. By September, plague and hunger were ravaging the city's defenders and inhabitants alike. On 27 October 1651, after Ireton had trained a battery of 28 siege guns on a vulnerable stretch of the town wall, Limerick surrendered. The works were then abandoned. They were not forgotten, however. When William III arrived before Limerick in August 1690 during the War of the Two Kings, the Jacobite garrison had reoccupied and refortified the same earthworks. The army chaplain George Story recorded both sieges in detail, noting that during the second Williamite attempt in 1691, the forts were retaken in a sharp action by detachments under Lieutenant-General Mackay and Count Nassau, after whom the forts were promptly renamed. The city surrendered on 3 October 1691, sealed by the treaty of capitulation that became one of the most disputed documents in Irish history.

The fort's physical presence diminished steadily after that. Its northern section had been levelled by the mid-eighteenth century, and William Eyres' city map of around 1752 shows only the southern half remaining, with the added confusion of a mislabelled index. In 1834, the construction of a reservoir removed most of what was left. Archaeological monitoring carried out in 1996 uncovered remnants of a cobbled road within the surviving western section, and the excavator noted that whatever earthworks endured into the modern period were most likely removed during subsequent housing development. The late nineteenth-century Ordnance Survey at 1:2500 scale recorded the western section and south-eastern bastion as still partially visible, which provides at least a cartographic reference point for anyone curious enough to cross-reference old maps against the present landscape around Singland Hill.