Cool! Thanks for the ping!
My pleasure. I’m pretty sure I’d never heard of it myself, and I’m sure there are hundreds, or perhaps thousands, of such enigmatic sites. The best known (I think) is Mystery Hill in, hmm, VT? NH? It’s a large site, although for the most part only the big structures on the crown of the hill are talked about. It has often been claimed (and probably still is) that it was built by some family as a “colonial root cellar” and foundation, but the fact is, it wasn’t — and verifying this is a radiocarbon date from a hearth inside the structure, yielding a 2000 BC date.