https://en.wikipedia.org/wiki/San_Pietro_in_Vincoli
watched a walk thru of this church today on the video-puterscreen, and the guy (who spoke spanish, but I translated it) talked about San Petro and also . . . the chains that are in the building. There was a Cross of Saint Peter in that church near where the chains are.
also very strange to find that one of the links to the chain is in Burlington (VT) very strange.
I was floored.