McGanns Cave, located on the northwest flank of Aillwee Hill, Co. Clare, consists of a single horizontal passage some 204 m. long. The original passage was of considerable dimensions but is now largely infilled over much of its length. The cave is almost fossil but once functioned as a major resurgence, possibly carrying glacial meltwater for a relatively short time. The cave is little influenced by local geological or hydrological controls and thus differs markedly from the majority of caves in this area of Co. Clare.