Very helpful to have plan-G installed, which shows google maps (terrain view) in one view. Look for the "wrinkled" parts:
Olympic Peninnsula, Washington state. (Seattle)
The cascades east of there (Seattle)
Glacier National park (Kalispel)
almost anywhere in the Rockies (Idaho, Montana, Wyoming, Colorado, New Mexico, Arizona)
The Sierras of California.
The Alps in France, Italy, Switzerland, Austria.
You can also Google "scenic drives" and get lots of scenic suggestions, usually because of the terrain.
Google "canyons, Mountan ranges" etc.
Hooked since FS4... now flying: FSX Acceleration on Win7/64, Core Duo E8400; GA-EP45-DS3R; GTX 460-768MB; 4G RAM; Freezer 7 Pro