Wanting to capture a nighttime panoramic photograph of Toledo, Spain in which darker areas were illuminated, the Photographic Association of Toledo decided to eschew HDR and attempt something new — light-painting on an epic scale. They enlisted the help of 50 association photographers who strolled around the city firing off their flashes multiple times per minute. The resulting photograph was illuminated by over 3000 flashes covering 100K square meters. Wowzers!
This Spanish blog has a detailed account of how the photograph was made, though you’ll have to have it machine-translated if you can’t read Spanish.