In Groton, CT there's Gungywamp, which has a chamber and all kinds of stuff. I haven't been there yet.
Lumix (welcome) do you have a focus on these chambers? You've posted a couple pictures of different locations. If you're trying to map out all these chambers, there's one on Mathewson Mill Rd. in Preston CT that looks almost exactly like the one you posted off rt. 102 in the other topic.