will be disqualified.
For this competition, you must create an area of interest for Combine transport. This could mean some sort of railroad station, a port, some sort of air/space port or a combination of some or all of these things. You are not required to build a working transport method to be used by the player. The main intention is to make a map that you can move around and look at, not drive through it (extra points if you can actually make moving Trains or Combine helicopters flying around, although the "building" or "buildings" are much more important).
You can of course use any of the Combine textures and props, but the map is not restricted to that theme. An old human railway station transformed by the Combine could also do the job. The Hub can be anywhere (city, coast, snowy mountains etc.)
In conclusion: as stated above, you have the choice to make it feel alive and have some sort of singleplayer story (with combine soldiers etc.) or go for an abandoned feel with more attention to eye candy.
Note carefully that this is a Source competition, and <span style="color: #ff0000">read the rules carefully!</span> Entries breaching the restrictions