The rectangular tower, which rises two storeys from its sturdy battered base, represents the kind of defensive structure that once dotted the Irish landscape during the medieval period. Though now heavily overgrown with vegetation, the castle's essential features remain visible to those willing to brave the boat journey across the lough.

The tower's construction showcases typical medieval Irish defensive architecture, with a barrel vault covering the ground floor; a structural feature that provided both strength and fire resistance. The original entrance can still be traced in the south wall, whilst the interior preserves two intramural staircases: one in the east wall ascending to the first floor, and another in the north wall that once provided access to the roof level. These narrow passages, built directly into the thick walls, allowed defenders to move quickly between levels whilst maintaining the structure's defensive integrity.

Historical accounts, including those by Davies, have documented the castle's architectural details, though accessing the site today requires some determination given the dense vegetation that has reclaimed much of the small island. The O'Reillys, who controlled much of County Cavan during the medieval period, likely chose this isolated location for its natural defences; the surrounding waters of Lough Sheelin providing an additional barrier against potential attackers. Despite centuries of exposure to the elements and abandonment, Crover Old Castle endures as a tangible link to Cavan's turbulent medieval past.