Broadway theater tour

I remember visiting New York many years ago and going on a Theatre District walking tour that actually took you inside two Broadway theaters (I believe one of them was the Eugene O'Neill, and this was around the time of The Full Monty). I've been looking online for that tour (or something similar) but I can't find anything.

Does anyone know of a walking tour that takes you inside Broadway theaters? Or individual theaters that offer tours themselves?

I've been on the Lincoln Center tour which takes you inside the Vivian Beaumont, but I would be interested in touring some of the other Broadway theaters, as well.

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I know I took one about ten years ago as well, but this one took us inside the Hirschfield (Martin Beck then) and Walter Kerr theatres. I want to say it had something to do with the Marquis hotel (or at least that's where the tour started) but I'm not entirely certain.

I saw an ad for a Spider-Man behind the scenes VIP tour on Ticketmaster, but I don't know anything about it. Not Broadway, but I know Radio City Music Hall and Carnegie Hall have tours.