Stumbled upon this article on Pollstar. Apparently LIU Brooklyn turned a theatre into their gym years ago, and now they're going to convert it back. Based on the article it sounds like they'll use it more for other performing arts besides theatre, but it's a cool story nonetheless! I'm impressed someone had the foresight to take measures that would allow for such a relatively easy conversion back to its original state - or maybe that was just cheaper?
LIU Paramount Theater, Long Used As A Gym, To Be Restored