Here's a cool new tool to show growth and decline of almost 600 world cities since 1950...with projections to 2050
http://www.visualizing.org/html5/19716
and add to it this quick look at the 16 largest cities over the course of human history
http://www.businessinsider.com/largest-cities-in-history-2011-4#
Cool... not sure what I am looking at tho. :)