Same thing I think. End of the same building. Still apparently accessible through the Café De Paris Casino entrance also.
However, I believe there are two identical rooms (mirror image) at either side of the main building, and the pic you showed is wrongly labelled. That slot area is the right hand side of the building when you look across Casino Square. Here is the left hand Salon D'Europe with it's famous double roulette tables (where I had my win).

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Interesting, when searching images I came across this pic supposedly of the main casino.

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Either this is some extension or a huge room I never saw? (Strange as I've been there 3 times).
This is what I recall as the main room with the famous rectangular glass ceiling. Everything else was smaller salons, loads of them. Maybe they opened a lot of it out?

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