The more innovative cities become, the more talented people want to live in them. The more talented people arrive, the more innovation they generate. Take Ryan Gravel, a quintessential example of how minor players with off-the-wall ideas are tweaking their own cities according to a new set of ideals. In 1999, Gravel needed a thesis topic for his joint degree in architecture and urban planning. The 27-year-old grad student knew one thing about Atlanta: It was a bitch to get around. So he created a plan for the BeltLine, a 22-mile “emerald necklace” of parks, light rail and new development encircling the city. Today, it’s actually being built. The improbable project seems to have come to fruition through sheer enthusiasm: “Neighborhood groups, church groups, pedestrian advocacy organizations, cycling organizations,” says Gravel. “There was a huge groundswell of public support, and it came from the bottom up. The people of Atlanta owned this project before the mayor did.