“The 320 gigapixel image – taken by expert photography firm 360Cities – comprises 48,640 individual frames which have been collated into a single panorama by a supercomputer. The pictures were taken using Canon EOS 7D cameras with EF 400mm f/2.8 IS II USM lenses and Extender EF 2x III teleconverters driven by special Rodeon VR Head ST robotic panorama heads from the Clausscompany in Germany.
If printed at normal resolution, the photo would be 98 meters long (323 feet) and 23 meters high (77 feet) – almost as big as Buckingham Palace.”

Click the link to view BT London Gigapixel Panorama 2013.