The record on the RCAHMS database is full of measurements of the hut circles, cairns and field systems here at the foot of Benachally.
Above here, somewhere..
In the face of Benachally, which looks towards the east, there is a cave of considerable magnitude. It is called the Drap, or Drop, from the water oozing through the crannies, and perpetually dropping from the roof. Below the Drop, and near the foot of the mountain, is a cove, called Henry's Hole, from its having been in former times the hiding-place of robbers or plunderers of that name.
One would assume the inhabitants (at least the smaller ones) of these huts would have known such caves. More hut circles, cairns and cup-marked rocks lie on the other side of the reservoir to the NE.
from p1025 of the New Statistical Account, v10 (Perth) 1845.