Living in Niederzier, we are surrounded by opencast mines. One of them is the Inden opencast mine just about a 10 minute drive away. After RWE (the power company that is mining there) is done, the former mining areas will be renaturalised. Some turned into farmland, some became the new riverbed of the Inde. There are really nice walking trails along the Inde as long as you don’t mind the bucket wheel excavator and the power plant at the skyline! In the future there will be a lake, too. It will take 30-35 years to fill it up with water!
So here are some links with more information and some photos I took!