control tower

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A tower at an airfield from which air traffic is controlled by radio and observed physically and by radar.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun aviation An airport building from which the air traffic control unit monitors and directs the movement of aircraft on and around the airport.
• noun An enclosed, raised structure occupied by one or more persons who operate or exercise control over railway traffic, ship movement, a racetrack, machinery, etc.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a tower with an elevated workspace enclosed in glass for the visual observation of aircraft around an airport