This plan has an On30 loop with two sidings on the upper level. The plan uses Kato HO Unitrack which is great to work with and looks good for On30 to me, though is not protypical in the tie spacing. But another track type could be used instead. The On30 has a long trestle that actually runs between tracks of the Fastrack O. I envision this track being supported by 3/4" PVC pipe spray painted to look like concrete pillars, but another technique could be used.
Down at the river level, a Fastrack O-36 loop has some Atlas O for the bridges. The lower main lines are all O-36 except for short O-84 sections leading into the tunnel at the top left.
I had in mind the river valley East of Portland Oregon along the Columbia River, where trains run along the river itself, and also above on the higher elevation. The middle and western part of the state is more arid grassland, with few trees. Instead of regular mainline trains on the higher elevation, I took the liberty of subsituting On30. Bridges cross the river at irregular intervals and at different elevations.
The topography starts at the river at the lowest elevation, and is built up using 1" and 2" thick foam sheets, to climb from 0" to 7" in height. With the lowest part the river running through the middle of the layout, the layout has an unusual and interesting look. There is one tunnel, and a number of places with sheer rock walls which can be done using the foam easily.
The easy construction techniques make this a good first layout plan, perhaps with Fastrack rather than Atlas-O for the bridges [connecting Fastrack and Atlas-O is not hard, but perhaps more than a first-timer would want to attempt]. If the foundation is a 2" thick sheet of foam, then the entire layout is easily portable (removing the trains and buildings). I would think that Lionel LionChief and LC+ locos would be fine on the O-36 Fastrack, and Bachmann On30 trains are detailed yet inexpensive, and run very smooth.
