The answer to the August 10 challenge -- which 115 people got right -- was the control tower at Wittman Regional Airport in Oshkosh, Wis., which during the annual EAA AirVenture fly-in air show becomes the world's busiest control tower.
August 19, 2013 4:00 AM PDT
Photo by: Daniel Terdiman/CNET
| Caption by: Daniel Terdiman
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