Hanga/Port

 First, we have the Hangar/Port. The entrance. 

1) Customs

2) Cargo delivery and storage

3) Stations connecting rails to other arcologies

4) Military is stationed here, not any further up into the arcology if it resembles anything like a liberal democracy

5) A few storefronts and bars, your subway musicians are here, more barbers than salons in terms of the business you see, but generally they explicitly don't want it to be too comfortable.

6) this might be where detention centers are held, even for residential disturbances?

7) Does it extend underground?

8) is this the main headquarters for security?

9) Sort of secretly pays for the arcology as it's billboard heavy? though I wonder if that conflicts with the "customs" or "security" aspect, or it helps?