Move forward to other category for inclusion:
Wachau Cultural Landscape - for its imposing abbeys
We currently have the Wachau as a Yes and the Middle Rhine Valley as a maybe. Can this be justified? The Rhine Valley played an important role in the development of romantic historicism. It also played a role in literature and art of the 19th century. Moreover, it has the largest concentration of mediaeval fortresses anywhere in Europe and is much longer than the Wachau. Having lived in Vienna I am very fond of the Wachau, but should it be ranked higher?
The Rhine valley is nice, but not really that spectacular (in my view, but maybe I've crossed it too often by train). Yes, it's filled with medieval castles, but so are other parts of Germany (and the ones in the Rhine valley are not necessarily the most picturesque). Probably you can say the same about Wachau, but what makes Wachau superior in my view are the monasteries, and in particular Melk.