The Moselle is a river that flows through France towards Germany. It is a beautiful area to drive to with your RV. Along the river you will find plenty of campsites by the water. Furthermore, there are all kinds of villages with castles you can visit.
For example, one well-known place is the village of Cochem. An old German town with classic houses. On top of the mountain you can visit the castle of Cochem, which gives you a fantastic view of the Moselle. A nice campsite nearby is Camping Happy Holiday. It's a fairly basic campground, but there's usually room and you're nicely situated by the water. You can then easily visit Cochem by bike.
