A week ago I posted the population data of the 20 largest metropolitan areas. Population is interesting when you're thinking about city economies, cultures, influence, etc.; but it doesn't tell you a damn thing about how far you'd have to walk to get from downtown to midtown, from the Bay to the breakers, or from the Fenway to the Beacon Hill. To compare city sizes, Rob Cockerham has developed a niftly little web page that shows two same-scale city maps side by side. I'd be nice to see more cities, but it's worth a quick look.