First documented in the Down Survey of 1655–6, this circular earthwork spans roughly 30 metres in diameter and consists of an earthen bank with an external drain running alongside it. Though the 1909 Ordnance Survey six-inch map clearly marked its presence, time has not been kind to these features; large boulders now obscure much of the original earthwork, and the entrance to the enclosure has become impossible to identify.

The site likely served as more than just a simple field boundary or livestock enclosure. Taylor’s 1783 map of County Kildare depicts a fairly substantial house at this location, suggesting the earthwork may have formed part of a larger domestic complex. Whether this was a defended farmstead, a small manor house, or perhaps an earlier structure that was later built upon remains unclear, though the presence of both the enclosure and the later house points to continuous occupation of this spot over several centuries.

Today, visitors to the area will find only subtle traces of this past; the house shown on Taylor’s map has long since been levelled, leaving just the circular earthwork as evidence of Ballycollen’s former significance. These remains, compiled and recorded by researchers including Gearóid Conroy, offer a tangible link to Ireland’s complex layers of settlement and land use, from the tumultuous period of the Down Survey through to the more settled agricultural landscape of the late 18th century.