This rectangular stone foundation, measuring just over five metres long and three metres wide, sits immediately northwest of the southwestern entrance to a larger hillfort enclosure known as Reachlainn Uí Bhirn. The positioning is no accident; whoever built this structure wanted eyes on everyone coming and going through this particular entrance.

Archaeological surveys suggest the building’s entrance was located in its southern corner, perfectly aligned to monitor access to the fortified knoll above. While time and stone robbing have taken their toll on the structure, leaving only degraded foundations visible today, the site’s purpose seems clear from its placement. Some archaeologists, including Michael Herity writing in 1995, have proposed it may have served dual purposes, functioning as both a guard house for security and possibly a guest house for visitors to the hillfort.

The site forms part of a larger complex of structures around the enclosure, with at least two other house sites visible nearby when viewed from the east. These remnants, photographed extensively in the 1980s, offer a glimpse into how Iron Age or early medieval communities organised their defensive settlements. The careful positioning of buildings, the control of access points, and the commanding views across the Donegal countryside all speak to a sophisticated understanding of both architecture and security in ancient Ireland.