Poll Ballynahown is situated on the western side of Knockauns near Poulomega. It was opened up, explored and surveyed by the University of Bristol Spelaeological Society in July 1968. The cave consists of a single, meandering stream passage which courses S.S.W. for 1,480 ft. to “Choir Chamber”. From here the stream turns sharply and follows the 16° joint for 345 ft. to a 70 ft. pitch. A further 228 ft. of meandering stream passage, at the bottom, terminates in a sump. The total length of the system is 2,085 ft. and the depth about 250 ft.