File talk:Fontaine Futuristics seen from Seafloor.jpg

The top 1/3 of that building likely is a tower (common art deco feature) done to be impressive but not actually part of the building interior (most of  the other floors see below are have not even a blocked path/door leading to them, but at least are sized dimensionally  to possibly exist). Utilities and such could still be placed up in that volume.