Answer: London

To promote the 2012 Olympics, British Telecom enlisted the help of photographers Jeffrey Martin, Holger Schulze, and Tom Mills to create the largest panoramic digital photograph ever taken of a city.

Shot from the top of the BT Tower, the image was created from 48,640 individual photos captured with four Canon EOS 7D cameras with 400mm lenses outfitted with robotic mounts. The collection of photos took three days to capture and three months to process on a Fujitsu Celsius workstation to fully render into an interactive panoramic image.

The end result was more than worth the wait, however, as the 320 gigapixel image has such high resolution that you can zoom in from the top of the BT Tower over two miles across London and count the individual windows on the spire of Big Ben. If printed at full resolution the image would be 323 feet long and 77 feet tall.

The panorama remains online as part of a collection of large city panoramas created by the same team; you can explore London with their panorama viewer here.