Pollatoomary (Pollflanagan)

Cave details

< 1 km
Vertical range:
103 m
Co. Mayo

A completely flooded cave, which serves as the resurgence for Aille River Cave. The entire depth is underwater, making it currently the deepest sump in Ireland (and the British Isles), dived to 103m depth. The unexplored passage continues visibly deeper, and exploration is still in progress. With the entrance at an approximate altitude of 36 metres (about 4 metres below the lowest point on the road downstream), the lowest point in the cave is about 67 metres below sea level, the deepest known point of any cave in the British Isles. (If the altitude of the entrance is as high as 40 metres - it cannot be any higher, since the lowest river surface inside Aille River Cave is at 40 metres - the lowest point would be at 63 metres depth, which would be the second deepest known point of any cave in the British Isles, after Pollindre.)