Not a cave in the geological sense, most likely, but a souterrain, one of those dry-stone underground passages built during the early medieval period in Ireland, typically used for cold storage, refuge, or both. These structures were constructed without mortar, roofed with large flat stones, and covered over with earth, leaving little trace at ground level beyond a slight depression or a collapse in the soil.

The tradition was recorded in the County Louth Archaeological Journal in 1942, placing it in a field adjacent to a known earthwork. That earthwork, catalogued separately, suggests the broader area around Proleek Acres was a site of some organised activity in the early medieval period. The pairing of an earthwork with a nearby souterrain is not unusual; the two features often occur together, the souterrain serving the enclosed settlement above. What makes this particular case quietly interesting is that the souterrain, if it exists, has not been confirmed archaeologically. It lives, for now, entirely in local memory and a passing journal reference from over eighty years ago.