Also known as the Mote of Monacoghlan or the Rath of Laragh, this medieval fortification consists of a flat-topped motte roughly 11.5 metres in diameter at its summit and rising 8 to 9 metres high. The mound is encircled by a berm, a flat ledge that features the remains of a wide stone wall along its outer edge, except on the southeastern side. Traces of a defensive ditch, or fosse, can still be seen around the base of the berm, whilst a ridge to the east may have served as a bailey; the defended courtyard typical of these castle designs.

The monument appears quite different today from how it looked in centuries past. An 18th-century illustration by Edward Ledwich shows a much more complex structure, with the motte positioned at the northern end of a ridge, accompanied by two baileys at different levels. The upper bailey’s base was surrounded by a fosse on all sides except the southeast, where a lower bailey contained a well and could be entered through an eastern gateway. The southwestern side of the ridge was defended by three earthen ramparts with corresponding ditches, with the innermost bank enclosing the outer bailey. A wall is shown extending from the southeast side of the motte towards this outer area.

In 1905, Canon Carrigan documented intriguing evidence of later occupation at the site. About 20 yards north of the motte’s base, he noted a quarter-acre plot known as “the Friar’s garden”, its boundaries still clearly marked at that time. Between this garden and the motte were traces of what appeared to be a house, presumably the residence of the friar who gave the garden its name. These earthworks likely represent the remains of a deserted medieval settlement associated with the castle. From its commanding position, the castle would have enjoyed excellent views across the surrounding countryside, including sight of Kilbreedy Castle to the northwest, demonstrating the strategic importance of this location in medieval Laois.