Lighting

Last month saw the debut of one of the world's longest footbridges, which also happens to be 100% solar-powered. 36,500 people are projected to walk across the bridge each week.

Fighting gang crime in Los Angeles is as easy as leaving the lights on at neighborhood parks.

What light is right? How much is too much? These questions don't typically get asked in cities, as they simply rely on what they've always done. But now the Municipal Art Society in New York is bringing these issues to the table.