Lionel developed a Disappearing Mountain layout in the 1950's to highlight its newest innovation "Magnetraction". Basically the train went into the mountain and down a steep 1 loop helix, then back up and out the other side of the mountain. The train was long enough so the caboose entered the mountain just before the engine came out. Mine is a variation on the theme on the inside siding of loop 3. The train is long enough so the engine starts coming out just before the caboose goes in, so it has more of an accordion effect. The outside siding has a Lionel stop train station. As the train engine passes the station, it stops for a period of time (adjustable in the station) to drop off passengers, then resumes. Here are some pictures of the helix being built and the finished loop, with a video showing how it works.
Base of module dropped about 5 inches below table top to allow room for helix
Module painted, and supports added for upper level of mountain.
Helix completed and train running. Notice engine entering mountain as caboose comes out.
Temporary mountain and outside loop laid in. The mountain will continue to the left to the edge of the layout after the 2 tracks next to the current mountain, then a loop of track and a village will be located on top.
