“Paris from the Eiffel Tower” by Ben Heine. As he describes it:

This is a view of Paris from the top of the Eiffel Tower (324 meters/1063 feet high). The image is huge, please enlarge for full details by clicking here (original size!). It actually is a montage of 12 photos (and no fish eye, no wide angle…). It took me 2 days of work. (You’ll need to enlarge the image to see properly some of the monuments that have notes…)

The giant version he links to is really giant — over 9000 pixels in width. It is now my desktop.