Rumbling Hole is a cave on Leck Fell, in Lancashire, England. Its entrance is a 50-metre (160 ft) deep fenced shaft, and it rapidly descends a series of pitches to a low aqueous passage that has been connected to Lost Johns' Cave. It is part of the Three Counties System, an 87 kilometres (54 mi) cave system which spans the borders of Cumbria, Lancashire, and North Yorkshire.[1]