Milling about in the woods

While hiking along the Vernooy Kill Falls in Rochester, I spotted what appeared to be a chimney in the distance. See it up there on the left?

It's quite common to stumble upon lone fireplaces in the forest. It's also common for my eyes to play tricks on me. When I got closer and my angle of vision had changed, I could clearly see that it was a massive wall.

Here it is from the opposite side. It's at least 12 feet high and double that in length.

Could this be the remnant of one of the first handball courts in the Catskills? Not likely, though that wall is just begging to be hit with a pink Spaldeen.  I later found out that Cornelius VerNooy, a Revolutionary War veteran and early settler, was responsible for this structure. About 250 years ago he built the first gristmill in the region. All that remains of it is this enormous (and old!) wall.