You find cycle tracks and suggestions on a cycle tour here. Riding a bike in the Spreewald is not heavy because there are no important gradients. You look for yours driving cycle tour end depending on condition, starting point and path length.
Card with waterways, walks, Skater trails and bike driven distances in the Spreewald. This map contains Burg with Oberspreewald to Lübben and partly Cottbus. Almost one "must" for cyclist, hiker or canoeist.