For the past 25 years or so, the photography department at Rochester Institute of Technology have hosted what they call the Big Shot Project.
They pick a landmark building and organized a large group of people to come out and light up the building at night using flashlights and camera flashes. Last night they did the National Museum of Play, and I went along to help out.
Here's the final shot. The link below has they rest of the shots from the past 20+ years.
http://www.rit.edu/cias/bigshot/