steepest street in the world in Wales recently made official.. Baldwin street in New Zealand had the title since 1987, the street in Wales has been there over a thousand years so Baldwin street never really was the steepest to begin with, and I'd imagine ffordd pen llech will have it's title taken as well when they measure the gradient somehwere else, I'd imagine there is postentially hundreds if not thousands of streets around the world who's gradient has not yet been measured.