 In one instance, the central purpose of the Rheingauer Gebück, a 38-kilometre fence erected in the 12th century, may have been to close down a German ridgeway and force traffic onto the Rhine river.Many ridgeways have continued in use with macadam or paved surfaces in modern times.Others fell into disuse when more level paved routes, either along valley bottoms or cut transversely along hillsides, were built parallel to them.