Hartsfield-Jackson Atlanta International Airport (ATL) is the busiest airport in the world when ranked by passenger traffic. It is located seven miles south of downtown Atlanta.
For such a busy airport, it's remarkably centralized. All passengers are funneled through the same main terminal, regardless of which far-flung concourse at which their plane may have landed. Rental car companies serving the airport are located in a central facility two stops and a five-minute ride from the terminal via ATL's SkyTrain. The facility is located on the other side of I-85 from the airport and is not within walking distance.