I saw this image posted in another question. What airport is this?
This image was taken at London Gatwick. The bridge connects two portions of the North Terminal, right next to where the North Terminal is labeled on this map:
This is not the only airport to have such a feature, though. Denver International also has a bridge (picture) over the taxiway connecting the terminal building with Concourse A. This one is not as high as the bridge at Gatwick and can't clear anything larger than a 737.