The name alone signals that something grim once happened here. A gibbet was a post or frame from which the bodies of executed criminals were publicly displayed, and the word attached to this low rise on the western edge of the Curragh of Kildare is not accidental. What survives today, however, is far older than any public hanging: a substantial prehistoric earthwork, a roughly circular enclosure about 56 metres across, defined by an earthen bank that still stands some three metres above the interior ground level and rises to around six metres on its outer face. The bank is some 15 metres wide at its base, which gives some sense of the effort originally invested in its construction. A broad outer fosse, the ditch that would have been dug to provide material for the bank, runs around the outside, and a single entrance faces east.

A rath, in Irish archaeological usage, is a ringfort, the most common type of early medieval settlement enclosure in the country, typically built to protect a farmstead and its livestock. The dimensions here are on the larger end of the scale, and the site sits on a commanding low rise with open views across the flat grassland of the Curragh. Its later association with execution may reflect a pattern common across Ireland, where prehistoric earthworks were repurposed by later communities as places of assembly, justice, or punishment, partly because their age and scale already carried a kind of authority. The site was recorded by Seán P. Ó Ríordáin in 1950, and the surviving earthwork has not escaped the attentions of the nearby military camp. Several concrete pill-boxes, the small fortified emplacements associated with twentieth-century defensive preparations, have been inserted into the enclosing bank, disturbing its profile in places but leaving the overall form of the monument still legible.