To celebrate their steepest street in the world ... 9. Waipi'o Valley Road, Big Island, Hawaii (25%) This treacherous road on Hawaii’s Big Island averages to a 25 percent gradient with parts ...

The Guinness World Records has an award for the steepest road in the world, and Baldwin Street of New Zealand is the current title holder. Often, if a city boasts one of the top sloping streets, ...