Hm. It's a tough one, for sure. Since this is a train show, it has to really be mostly about the train, so that makes it tougher. Otherwise I would say, why not have a few tables at one end, with a space between them, making up a mountain, you could use paper to make a steep cliff side going from the table to the floor. The train could run on the tables, making a loop on the tables on one side of the bridge, cross over it, make another loop, and cross it going the other way. There could be a town and a mining camp up there on the tables. Then the river could continue on along the floor and there could be indian camps, forts, etc, set up on the floor. Does that make sense? I don't know if I explained it well.