The South Platte River starts high in the Rocky Mountains of Colorado and flows through the heart of Denver on its way to the Great Plains. The waterway went from being a polluted, noxious cesspool, to some of the most sought-after real estate in the city. For decades, the river was so ignored that many didn’t know—or even care—that the South Platte ran right through downtown. All it took was a flood of biblical proportion to get their attention.