Souterrains, which are artificial underground chambers and tunnels typically built during the early medieval period, were constructed for purposes that still generate debate among archaeologists, with theories ranging from food storage to refuge in times of raid or conflict. They were built without mortar, using carefully placed dry-stone walling and large capstones overhead, and their entrances were often deliberately concealed. The one at Rubble belongs to this tradition, a subterranean structure quietly waiting in a county that contains dozens of similar monuments, most of them unremarked upon by anyone passing above.