Wellllll, the simplest plan would be an oval with a viewblock down the middle so you could have two separate scenes. Yard and industries on one side, country / desert / mountains on the other. Or one side devoted to multitrack staging while ops run on the "visible" side.
I prefer donut or around-the-walls layouts but I'm doing an oval with staging in N-scale on a hollow core door, more or less as an experiment, and for when I want a break from my HO shelf switcher. I also don't care for "spaghetti bowls" but some people love 'em. Your layout, your choice...