This just looks old.

Going north on Ringe Rd in Fitchburg, taking a right on Piper Rd, a few moments later this appears on the left, while a view south down an inlet to the Fitchburg Reservoir appears on the right. If you right-click and open this in a new tab and magnify you'll see how the rocks are weathered, moss covered, and deeply covered with dead leaves. It is the oldest looking structure I can think of. So I think this is old.