Walking is one of the most overlooked forms of physical activity. It costs nothing, burns calories, allows you to multi-task, all the while doubling as a mode of transportation that doesn't leave you sweaty or needing time to recover.<p>I was about to say that not being able to walk to work - either because you live in a car-centric suburb, or because it's dangerous - is a nigh criminal failure of city planning.<p>On second thoughts, though, that's probably unfair. It's probably a case of demand driving planning, not the other way around. I can't blame city planners if people mostly prefer a large house in the suburbs, and are willing to pay for it with a 45-minute commute.