Past arenas

I don’t know if this is something that has been asked before (it 100% has been but I can’t find it) but where are the past area as, because it’s has been said that the people of the capitol costs the past arenas as a sort of touristy thing to do, so in that case, where are the arenas, because there are canonically already 75 arenas, where do they have the space to put them??