That’s Goddard’s lab, and prior to that, the electromagnetic library/lab. Goddard blew up stuff in Salisbury and was relocated because of the noise and obvious hazards. It’s not accessible to the public but by some streak of luck I got a chance to see the inside as a student over 20 years ago. Just happened to meet the right people, I guess. Not much to see but I wish they’d do something with it for historical purposes. It was just a frat-style hangout for Skulls with a sofa and some junk when I saw it. It connects to some tunnels that are probably pretty rough at this point.