Sir Henry Piers noted in 1682 that Faughalstown was the retiring place of the Earl of March, but historian Goddard H. Orpen later suggested the tradition might actually refer to Sir Thomas de Mortimer, who fled to Ireland in 1397 after being convicted of treason by the English Parliament. Sir Thomas, who had served as Chief Justice of the King’s Bench in 1382, sought refuge amongst the native Irish in Leinster with a warrant hanging over his head; a rather different character from Sir Edmund Mortimer, who had died years earlier in 1381.

The castle that once commanded this lakeside position was no modest fortification. According to an 1826 account, the fortress covered more than an acre, surrounded by deep ditches and comparable in scale to the mighty castle at Trim. By that time, however, only foundation lines remained visible beneath the grass, along with a small section of an auxiliary building. Local cottagers had already carted away much of the stone, leaving behind what is now classified as National Monument No. 610; a large rectangular earthwork set atop a massive embankment. The site retains impressive defensive features, including a wide, deep fosse on most sides whilst the western and southwestern edges drop dramatically to the lake below.

Today, visitors can still trace the outline of this once formidable stronghold through its earthen banks and depressions. The southeastern corner rises into a substantial mound where an Ordnance Survey triangulation station now sits, whilst the northwestern corner contains the ruins of what appears to have been a stairway leading to cellars or an undercroft. A rectangular platform runs along the northeastern interior, and various depressions mark where buildings once stood, including the outline of a rectangular house. Though only earthworks and fragments remain, the site still offers commanding views across Lough Derravaragh and the surrounding countryside, much as it would have done when the Mortimers, or whoever truly held this castle, watched for approaching friends or foes from its ramparts.