Hmmm, looks like it's gonna be pretty hugemungous you could use a mdf base and the innards of the mountain/cliff should be thick layered chunks of polystyrene, all coated off with a layer of papier maché, then add any detail with putty, be sure to "stab" at the papier maché before it dries to get jagd edges (geddit). You may want to consider a few details, such as dimensions of the finished thing, and be sure to draw down every detail of your idea so that you don't make it up as you go along. Moses still hasn't replied so i can't put the pics up yet. As for other ideas, i'm already planning my next dio, methinks something along the lines of troops at rest next to a busy road with military traffic somewhere in france. Well, gotta scoot, I'll be seeing you!