Aloys wrote:Hmm, the Antelope canyon, such a beautiful place..
"Aaaaah, Direbo. Such a peaceful place."
Is there something we should know, Aloys?

@red:
You'll need to sweep a profile curve. I haven't looked into any automated tools of Blender's for this, but here's one (of many) ways to do it manually:
Take a side view and add an empty mesh.
Hold down ctrl - now you can place a succession of connected vertices.
Draw a profile curve of a wall cut-section, or a canyon cutsection, if you want to do the walls on both sides at the same time.
Change to top view, select all vertices in the profile you drew and again hold down ctrl - now each left-click will extrude a copy of your profile and rotate it according to the direction you are "moving".
You can modify each section as you go, to assure a smooth change over time, or go in afterwards in sculpt- or proportional mode.