Way out of Spain, but still an official pilgrim route, is the Donau Radweg (Danube Bike Route) in Germany. The trail follows the Danube from one old town to the next, on a car free path. It features the yellow clam shell markers we all love. and has amenities such as inner tube vending machines and mini locking garages for your bike and gear so you can stroll around town and not worry about your stuff. It is very flat, and you'll see many older riders.