Known locally as Cromwell's Moat, it was in fact an artillery battery, raised so that Parliamentary forces could position cannon to pound the east wall and gate of the town. The mound is long gone, levelled sometime in the nineteenth century, yet the memory of what happened around it did not disappear quietly. When workers began disturbing the ground near the old town wall in the early 1800s, they turned up human bones, horses' bones, horseshoes, pistols, and other equipment of war, physical traces of a siege that had left its mark well beneath the surface.

The battery appears by name on Thomas Stuish's map of 1681, labelled 'Cromels Battery', which places it firmly in the landscape less than three decades after the Cromwellian campaigns in Ireland. The historian Carrigan, writing in 1905, described it as a smaller counterpart to the medieval motte at the opposite end of the town, a motte being an earthen mound of the kind used as the raised platform of an early Norman castle. The battery mound, by contrast, was a feature of much more recent and brutal origin. Accounts differ slightly on when exactly it was demolished: Carrigan gave a date of around 1850, while Kennedy, writing in 1984, placed the destruction earlier in the nineteenth century, attributing it to Callan corporation during works to enclose the fair green with a wall. A local archaeologist, Thomas Shelly, had carried out excavations on the mound before its final removal, and reportedly found traces of masonry and stone wall construction within it, though nothing else of particular note. When the first Ordnance Survey six-inch map was produced in 1839, the mound itself went unrecorded, yet a trigonometrical station marked at 280 feet in what is likely the same location suggests the elevated ground was still present and being made use of at that point.