Milky Roads (literally translated as "River of Clouds") are artificial routes in Skypiea, manufactured from clouds. One leads from the Heaven's Gate up to the White-White Sea.
Another connects Angel Island to the Upper Yard and then flows along the whole Upper Yard. People travel through the Milky Roads like through a river, usually using Dial-powered vessels. Milky Dials are also capable of fashioning Milky Roads, which the White Berets use to subdue criminals.