Summary of site:
Cradle Hole is one of the largest features in all the karst landscapes of Northern Ireland. It was formed when a large cavern, or perhaps a complex of smaller caverns, collapsed to form this huge doline, over 100m long by 60m wide and 35m deep. The river responsible for the active development of the cave system is the Aghinrawn, which flows to the foot of Monastir Cliff before vanishing underground. It reappears to surface view flowing across the floor of the Hole.
From the doline, both upper and lower courses of the river can be followed. The distance from Monastir sink to Cradle Hole is about 1km and a little less than 500m of the course can be followed. This part of the system, Upper Cradle Hole, is entered at the southern end of the doline. A wade upstream through roomy passages and deep pools leads, after 75m, into a large boulder strewn chamber. This cavern is immediately east of Pollnagapple (a large shake hole on the moor above). The river continues upstream in a 10m wide passage for 140m where a climb leads to a ledge, beautifully decorated with cave formations. The main passage continues as a lake, 7m wide, for the next 70m, at which point the water meets the roof. Swimming enables small extensions to be reached, but there is still a considerable distance to Monastir Sink.
Lower Cradle Hole is entered at the north-east corner of Cradle Hole under a massive overhang. Immediately passages divide to left and right, all leading to the Main Chamber. There are many passages in this vicinity, at both high and low levels, with interesting but blind side passages, squeezes and crawls. The Main Chamber is over 160m long and 20m wide, with the river flowing across its floor. The Sruh Croppa River, passing underground above Catís Hole over a kilometre to the south west, joins the Aghinrawn about 100m along the Main Chamber, and the combined flow meets the roof about 60m beyond. In exceptionally dry conditions it is possible to swim into the Grand Gallery of Marble Arch Caves through a series of ducks but this route is not for the uninitiated.