Historical maps from 1835 show what was once a narrow rectangular building, roughly 30 metres long and 5 metres wide, with a distinctive square projection jutting out from its northwestern side. The site’s importance stretches back much further; a 17th century baronial map marks a tower here, suggesting this was once a formidable defensive structure in the Cavan landscape.

The castle’s ownership reads like a who’s who of local power struggles and colonial change. Originally held by the Magauran family, it passed to Hugh McCahir O’Reilly around 1600, just as English influence was tightening its grip on Ulster. During the Plantation of Ulster, the castle and its 300 acres were granted to Bryan McShane O’Reilly, before eventually ending up in the hands of John Blatcheford by 1664. This transfer of ownership mirrors the broader shifts in land control that characterised this turbulent period of Irish history.

Today, visitors to Lissanover will find only fragments of this once significant structure. The castle’s stones were largely removed in 1909, leaving behind grass covered banks that hint at the building’s original footprint. The sole surviving piece of masonry stands at the northeastern corner, now crowned by a tree that has taken root in the ancient stonework. Archaeological evidence suggests that parts of the medieval castle were likely incorporated into the later rectangular projection shown on 19th century maps, creating a palimpsest of different building phases that spanned several centuries.