By the way, Frankfurt’s population is ‘only’ 732,688 (31/12/15) compared with London which was 8,538,689 in 2014.
With best regards and sympathy to my old friend Frank, take it with a smile !
The Wasserkuppe is a mountain within the German state of Hesse. The (950 m (3,120 ft)) elevation, which is a large plateau formation, is the highest peak in the Rhön Mountains. https://en.wikipedia.org/wiki/Wasserkuppe