In some ways, this is the most accurate map of Washington, DC, I've seen: those colours represent the demographic breakdown of a divided city. Here's how the largest metropolitan areas in the US look after the same treatment.
Eric Fischer has created and compiled similar maps for the 40 largest cities in the US, based on 2000 US Census data. One dot equals 25 people, and each dot is colour-coded by race; white is pink, black is blue, Hispanic is orange and Asian is green. See if you can spot the city without checking the title:
New York, New York
San Francisco, California
Los Angeles, California
New Orleans, Louisiana
Fischer was inspired by Bill Rankin's map of Chicago that followed the same basic rubric. It's a fascinating way to look at a cities, a reminder that in some areas we're still more bento box than melting pot. I'd be even more interested to see how places have evolved over the decades. [Eric Fischer via Data Pointed]