#23 This is a bit wrong. This is the Landwasser viaduct, but It's not spanning across, nor being in the Engadin valley. However, this train does travel between Chur and the Engadin valley. I know because I did this train ride in 2006. Leaving that hole in the mountain and suddenly looking down from the viaduct was a chilling experience.

http://en.wikipedia.org/wiki/Landwasser_Viaduct