Dunmore Cave
Dunmore Cave (from Irish Dún Mór 'great fort') is a limestone solutional cave in Ballyfoyle, County Kilkenny, Ireland. It is formed in Lower Carboniferous (Viséan) limestone of the Clogrenan Formation. It is a show cave open to the public, particularly well known for its rich archaeological discoveries and for being the site of a Viking massacre in 928.
Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).