Built sometime in the 15th or 16th century, this tower house served as a stronghold for local Gaelic lords during a particularly turbulent period in Irish history. The castle’s strategic position allowed its inhabitants to monitor movements across the lake whilst maintaining defensive advantages against potential attackers.

The structure itself follows the typical design of Irish tower houses from this era; a rectangular stone building rising several storeys high with thick walls designed to withstand siege warfare. What remains today shows evidence of various defensive features including narrow arrow loops, murder holes above the entrance, and the remnants of a bawn wall that once enclosed the castle grounds. The castle changed hands multiple times throughout its history, passing between various branches of the Burke family and other local clans as power shifted in medieval Connacht.

Archaeological surveys have revealed interesting details about life at Deel Castle, including evidence of a boat slip that would have provided direct access to Lough Conn for fishing, transport, and quick escape if needed. The castle fell into ruin following the Cromwellian conquest of Ireland in the 1650s, when many such fortifications were deliberately destroyed to prevent their use by Irish rebels. Today, visitors can explore the atmospheric ruins and enjoy spectacular views across the lake, though care should be taken as the structure is unstable in places and there are no safety barriers.