Wuppertal is a basically in a narrow valley surrounded by steep hills (think SF steep). Building a train atop of the river was very space efficient and probably

Wuppertal is a basically in a narrow valley surrounded by steep hills (think SF steep). Building a train atop of the river was very space efficient and probably much cheaper than digging a subway on groundwater level. Also it doesn't interfere with other vehicles. Last but not least, the Schwebebahn is just a very enjoyable ride.