W.E.H.R.T - Hole in the Wall Traditional Cache

On the Warren to E. Haverhill Rail Trail.  Wonder why these holes are found in the rock cuts??

A 5 inch diamter plastic container painted camo brown Trail is used by ATVs, dirt bikes, and, in some sections, cars. Would not advise small cars attempt the trip from the N end of trail due to large wet potholes. However, you can drive pretty much anything from Gould Hill Rd (Weeks Crossing) up to Black Bog parking area. From there it is a short walk N..