There can be computer simulations of people, places & all sorts of things in general. Cities, worlds, galaxies & perhaps even a universe or a multi verse.
http://www.breathingearth.net,
http://en.wikipedia.org/wiki/Earth_Simulator,
http://www.bbc.co.uk/news/technology-12012082,
http://www.extremetech.com/extreme/108025-living-earth-simulator-will-simulate-the-entire-world
http://therealitycode.blogspot.ca/2011/03/matrix-1999.html
