If you fly in or near congested airspace, you might have wondered at the rhyme or reason to some of your IFR routings, or the vectors you were issued when receiving VFR flight following. A good way to remove some of the mystery is to visit an air traffic control center. Though your training provides the fundamentals of how the ATC system works, there is nothing like standing behind a controller and picturing the traffic within his or her airspace from the view on the radar screen. And if you're able to listen in on communications, you'll gain a first-hand appreciation for the need for pilots to listen and speak professionally. Some facilities are more accessible than others, so you might not be able to arrange a visit, but it is not forbidden, even after 9/11.