I had created a similar topic several months ago regarding mountains, gullys, and valleys (vertical modeling). The main difference from what I see in most people's layout is that I want to take the consist up one side of the ridge, go around a peak, follow the ridge, and then take the consist through a tunnel over a bridge and back to standard fair. I also wanted to take the landscape down through the base platform to create a gully that the bridge crossed over. My focus for the mountains would be more tree based than rock formation with trees lining the ascent rail on the far side to slightly obscure the consist.
Basically, I wanted to add as much depth as possible to the layout.