Is this the American city of the future? With a revitalized riverfront and booming downtown, Columbus is already one of the nation’s fastest-growing cities. Now, it’s poised to become the model for the future of innovative urban transportation, with self-driving shuttles carrying travelers along the Scioto Mile, which recently completed a massive revitalization, adding 33 acres of riverfront green space for festivals, water sports and outdoor art. (The newly opened National Veterans Memorial and Museum also sits on the Scioto Peninsula.)