An undated map held in the National Library of Ireland (Ms. 21.F. 35 (066)) marks this location with the word ‘castle’, suggesting that the grand house we see today wasn’t the first significant structure to occupy this spot. The map offers a tantalising glimpse into the area’s medieval past, when defensive fortifications dotted the Irish landscape.

Today, visitors to Rathsillagh might notice a substantial two-storey outbuilding that serves as a barn. This isn’t just any farm building; measuring approximately 30 metres in length and 15 metres wide, its stone walls average an impressive 1.5 metres thick. According to local historian S. Hickey, these robust dimensions suggest the structure may incorporate remnants of the original castle marked on that old map. Such repurposing of medieval buildings was common practice in Ireland, where practical farmers often found new uses for ancient stones rather than letting them go to waste.

The transformation from medieval castle to agricultural building tells a broader story about Ireland’s changing landscape over the centuries. As the need for defensive structures diminished, many castles were either abandoned or adapted for more peaceful purposes. At Rathsillagh, the possible castle remains have found a second life as part of a working farm, preserving something of the site’s ancient character whilst serving modern needs. This information was compiled by Gearóid Conroy and uploaded to historical records on 7 October 2013.