The collapse exposed a space just 1.2 metres long, 1.4 metres wide, and 1 metre high, cut directly from the earth rather than lined with stone. It is now inaccessible, which means most people who walk that hillside have no idea it is there at all.

The structure belongs to a category of monument known as a souterrain, an artificial underground passage or chamber found widely across early medieval Ireland, typically associated with nearby settlement sites. They were cut or built into the ground and used variously for storage, refuge, or as cool spaces for dairy produce. The example at Hollyhill is of the earth-cut type, meaning the chamber walls are simply the compacted soil itself rather than constructed from dry-stone walling, a form found in areas where the subsoil was stable enough to hold its shape. Its modest dimensions suggest a simple storage chamber rather than an extended passage system. The fact that it came to light not through excavation but through ground collapse is itself a reminder of how much of the Irish archaeological landscape remains invisible until the earth decides otherwise.