Complexes are basically a collection of prepared and secured modules that have been specialised.
A hiport is constructed from fine carbon-60 polymers. These form a lighter than air 'rope' that is anchored to the world and stretches into orbit. Lifts are attached to the line and run up and down between the orbit and the starbase.
This is used to allow positions in orbit to transfer items to and from a starbase.
Domes, caves, command, mines, hiports, orbital docks, terraforming and bunkers do not count towards enclosed space requirement.