re: Schroter Valley
It would be nice if you could provide us with references.
I'm looking at the book "A la découverte de la Lune" and on page 132, there's a chapter devoted to the Schroter Valley and the Cobra Head.
The valley is 5km large and 1 km deep (it depends where, too).
There's a rille within the valley and following the rille from the west, this one gets between 2 cliffs 240 m high, but the distance between them is in kilometers.