As if created by giant hand, the spoil tips left behind by the area's mining industry are rising up between the cities in Germany's Ruhr Valley. Visible even from far away, they give you an idea of how many rocks and how much earth was brought up to the surface here in the past centuries. Today, many of these sites serve as excellent training areas for mountain bikers. Take your pick from easy flow trails to tough routes requiring you to bring along more protection than just a helmet. Since some of these dumps rise up more than 100 meters above the surrounding area, you'll be able to collect quite some meters of altitude throughout one day of exercise. By the way: taking your bike out at sunset makes for an especially great time!