Okay, so the pics I took a while back all reside on my stricken Photobucket repository, so, having failed to take advantage of their attempt at extortion, I pretty much lost access to those. No matter, I took a few this evening and here you go:



This thing was one giant experiment, and the results are a mixed bag for sure. I wanted to build something that had the Lionel felt-soaked-in-white-glue look about it, but with nicer portals and some foam rock-work.
The structure of the tunnel is built out of one-inch foam panels I picked up at Lowes or HD. They sell the stuff in three-foot square pieces, so I bought four or five of those and built the basic structure.
I cut the portals from some pine scraps I had laying around in the shop, roughly cutting the opening using a hand-held jigsaw. If you look close, you can see they are somewhat misshapen, but then so are most of the felt tunnels I've seen over the years. I put a band of 1/4-inch basswood across the top to provide a bit of trim. The "LL" (Lionel Lines) keystone I made using a couple of foam applique letters I stole from the wife's craft box. I wanted liners in the tunnels for the first 8-10 inches, so I printed some brick-paper I found on the web somewhere, pasted it on matt-board, then glued it into the interior structure using more foam as a backer. Fortunately, the matt-board is bendable if you take care, so I got a reasonable curved interior.
The "rock" face is just more one-inch thick foam glued in layers, than an attempt to make it look like rock. I've watched a ton of YouTube videos on how to carve rock from foam, and the methods seem to vary widely. I would say my attempt looks pretty amateur compared to what I've seen on Murph's layout and a few others.
The top is just a bunch of foam partitions cut to a hill profile, than a combination of newspaper and paper towels soaked in thin Hydrocal for a hard surface. The intention was originally to paint it using Lionel's instructions they gave with their postwar portal set, but it didn't work too well, so I'm either going to tear it off and try again or just cover it with green lichen.
Anyway, there you go. Any questions, comments, or suggestions welcome.