ashenspooks:

In Council Crest Park in Portland, Oregon, at the top of the knoll there is a large paved circle enclosed by a short stone wall. The area has a couple of dedications on it, and there is a massive compass of inlaid marble paved into the area, so you know which way you’re looking. Stand on the west compass point and walk over to the wall it is pointing to. Now look at the stones that the wall is made of. Moving south along the wall, count 10 stones along the bottom row and then give the 11th stone a nice hard kick. As you will easily hear, this stone is hollow. The 11th stone is the only hollow one. Something is contained inside.

All the stones are hollow, they’re stone facing on a concrete core. The 11th stone does have an opening for a drainage outlet but it’s not the only one and nothing’s in there.