It is a souterrain, a type of structure built during the early medieval period in Ireland, typically by hand-cutting a trench into the earth, lining it with drystone walling, and roofing it with large capstones before covering the whole thing over again. The result is a hidden chamber or series of chambers that archaeologists believe served various purposes depending on the site, from cool storage for dairy produce to places of refuge in times of raid or conflict. What makes souterrains quietly compelling is how thoroughly they disappear into the landscape; a field that looks entirely ordinary may conceal one just a metre or two below the surface.