It’s 5 p.m. on a weekday, and you’re in traffic. Your eyes wander toward a flash of color above. It’s not some advertisement; it’s a vinyl re-creation of an oil painting by Charlotte’s Nicholas Napoletano. It is part of ArtPop, the program that puts local artwork on unoccupied billboards across the city. It’s made Charlotte into a 297-square-mile gallery, and it often has people saying, “Someone here made that?” The idea is so good, dozens of cities across the U.S. are adopting it, with Charlotte leading the way.