Damn, that's interesting!

Among all of the visual information published by the U.S. government, there may be no product with a higher information density than the Federal Aviation Administration’s (FAA) aviation maps. Intended for pilots, the FAA publishes free detailed maps of the entire U.S. airspace, and detailed maps of airports and their surroundings and updates them frequently. The density of the critical information layered on these maps is staggering, and it is a miracle that pilots can easily decipher these maps’ at a glance. But they can.