This strategic fortification once guarded an important river crossing point, working in tandem with Barnacor Castle on the opposite bank to control passage along the Inny. The Down Survey of 1655-59 depicts it as a tower house fortification, and historical records show it belonged to James Dillon, 1st Earl of Roscommon, in 1641 before the lands were redistributed to Captain Edmonds in 1653. The castle’s position on a triangular parcel of land, bounded by rivers on two sides and a water-filled defensive ditch on the third, made it nearly impossible to approach undetected.

By the time of the 1837 Ordnance Survey, the castle was already in ruins, described as a small rectangular structure with its long axis running northwest to southeast. The site originally featured two distinct earthwork platforms; a raised circular mound where the castle proper stood, and a flat rectangular enclosure surrounded by low earthen banks just to the south. Unfortunately, extensive river drainage works in 1975 obliterated much of these earthworks, with heavy machinery destroying the castle site itself whilst spreading spoil banks along the riverbanks, making it difficult to trace the original medieval layout.

What makes Cashlanalotta particularly intriguing is the complex system of earthworks visible in aerial photographs to the south and southeast of the castle ruins. These features include what appears to be a large rectangular enclosure and a series of linear earthworks that likely functioned as fishponds or water management channels. The earthworks seem designed to divert water from the Inny River through wide channels, suggesting a sophisticated medieval water management system that would have served both defensive and economic purposes. Though much has been lost to modern drainage schemes, the surviving traces hint at a once-significant fortified complex that controlled both river traffic and local resources at this important junction of county boundaries.