That's the Nantahala & Smoky Mountain Gorge RR, a 4x8 track plan from Linn Wescott's Kalmbach book "101 Track Plans for Model Railroaders," page 15. The spur at the bottom is not on the original plan.
There is a photo of a layout built from the plan in this thread:
If one is looking for a tiny layout with a really long run that isn't the normal twice around this is it. For years I wanted to build a 6x10 version of this.