I developed the track plan so that I could have two trains running at the same time.  The inner loop has a return loop so that trains can be turned.  I started with LGB track many years ago and had a large quantity of the small radius curves so I designed a plan that would look convincing.  The outer loop is 1500 series radius which can accommodate Moguls.  I don't plan on running anything larger.  I model the period of mid-thirties, steam only.  I like the smaller "tea kettle" locos that look better on small radius track.  The tunnels and structures are located so as to confuse the eye and diminish the dog bone loop shape.  Everything is weathered and customized.  I use lots of add-on details and air brush everything.  I model the foreground to higher level of detail than things in the distance.  Everything is highly detailed however so that it takes a while for the viewer to see everything. 

The layout is designed to be expanded by 100% by connecting to the stub turnouts shown above.  I used 1"x 4" bench work with the main horizontal surface 2" high density  foam insulation.  I love this technique.  It is easy to carve, cheap, fast and planting vegetation is simple,( just poke it in  the surface).  I have learned to carve and paint it to look like rocks.  All the scenery is carved foam.   Ground cover and details are the same as the small scale stuff, just more of it.