The opening measures roughly half a metre wide and a quarter of a metre tall, dropping about a metre into the earth before opening into a stone-built chamber with two creepways leading off it. A creepway, in the context of souterrains, is exactly what the name suggests: a low connecting passage designed to be crawled through rather than walked. The whole structure is currently inaccessible, which means the opening functions less as an entrance and more as a reminder that there is a great deal going on underground that visitors cannot reach.

A souterrain is an underground passage or chamber, typically dry-walled and roofed with large flat stones, built during the early medieval period in Ireland. They are found throughout the country, often inside ringforts, and are thought to have served as storage spaces or refuges. What makes the Garrane example quietly notable is that it is not alone: a second souterrain sits in the south-east quadrant of the same ringfort. In 1934, a researcher named Bowman recorded both features, describing them as lined with stones and covered with flagstones, essentially the same construction technique documented in the more recent inventory. The persistence of that description across decades, from a 1934 fieldwork note to a formal county inventory, suggests the site has remained largely undisturbed and unstudied in the intervening years.