One thing I wanted to have on my modular layout was a tunnel. It isn't prototypical for my area, but it looks good and is fun to run the trains through. Taking inspiration from the T-Trak web sites, I went with a two-module tunnel. On this first module the tunnel and mountain cover most of the track.
I started with white Styrofoam as the base of what would become the mountain forms. The inside of the tunnel was lined with flat pieces. I made sure I had plenty of clearance in case I want to go back and line the tunnel with something. I also made sure I could fit my hand in to retrieve derailed trains.
On both modules the upper half of the mountain will be removable. Cardboard seemed like a good choice for the bottom of the cover. It will be covered with additional pieces of Styrofoam to finish the slopes. My plan for the portals is to use the one from scalescenes.net. In the meantime a piece of cardboard stands in.
For some reason I haven't taken pictures of the plain Styrofoam. I hope to capture that on the second piece.
Once the Styrofoam pieces had been shaped and hot-glued into place I started covering them with paper towels soaked in diluted plaster mix. It took two sessions to get the majority covered. Some of the most exposed spots will be covered with paper towel soaked in white glue for strength.
The top is already starting to blend in with the base — at least from certain angles — but I'll still need to find ways to camouflage the cracks. Bushes, rocks, etc., will probably do the trick.
Southern Loops Tunnels in Western North Carolina.