Yes, i was speaking of the top, as i guess one team will spawn there, and one of the major issue in arena mapping is making the spawn points not campable. Other floors are great in terms of level-design, since there are two stairways for each. I'd maybe recomend to take care at the height of staircase ceilings, as its annoying to bump in a bloc when using the stairs. I'm also a bit concerned at how a player can camp both staiways of a floor at the same time, but I guess we'll need to try the map to figure out how it works.
Once again, it's DEFINITELY worth a try. Don't worry about me touching it, since from my point of view it's close to perfect : great level of detail, nice choices in design, nothing to add in my opinion... EXCEPT : what is this ugly thing written in water? Please use a proper font to sign your cool map and paste it in the watermap!!;)
Other than that, it seems really good. You should think to provide the txt file with spawn extensions for arena mode, this way people could host it easily.