Paul:
Many folks in the hobby run their trains in different ways. Some are "loop runners" which are folks who enjoy watching their trains "circling" or "looping" on tracks. Some of us are nuts, including me, set our layouts up in such a manner that they simulate a real life railroad. Meaning, a point to point scheme of track planning--lots of fun!
Our trains actually go somewhere; not just continuously travel the same loop. They also do something, and that is drop-off or pickup rail-cars along the way, as real trains do. Doing these things give you something to do. If you are just looping you can turn the trains on and just let them run pretty much unattended. Both the trains and you won't be doing too much and putting this as delicately as possible because it will rub many the wrong way, how long is it going to be interesting to watch the same train circle and for how long?
I've been in the hobby forty plus years and my personal observation is that sooner or later layouts that loop become dust catchers. Not true in every case, but in most every case. I made that same error for years.
You have a gold mine! You do NOT have to circle or loop. You have a HUGE space. The Pennsy has one of the PREMIER rail-fanning sites in the universe--THE HORSESHOE CURVE!!! If you aren't familiar, and I'll bet you are, there are four main lines, in the shape of a horseshoe, climbing/descending the mountains in Pennsylvania. I've seen many videos! This spot is like one of the coolest on the planet!
With all YOUR SPACE!!! You could arrange your track and pattern them after the world famous horseshoe curve! You can check out ENDLESS volumes about the horseshoe curve, the railroad and the area from a huge variety of sources beginning with the Internet. You could replicate that area. You would have many people want to come and see the layout and run it! If you are just circling, you won't get that kind of impact.
You could, in that basement, run your trains over and through the mountains and around the Horseshoe Curve! You would have one "end" to your railroad on one side of your mountains and the other "end" in an opposite place.
Think of two table forks: The tines are pointing away from each other and the handles are your main-line. Your train would travel from one set of times to the other. Then at the other, be turned around (turntable, wye or reverse loop) to return from it's point of origin.
Your railroad would have Plausibility (believably) based on reality. Your railroad would serve a Purpose--delivering goods and people across Pennsylvania--and you would have Participation--meaning direct involvement and fun! controlling your trains across the and thru the Curve! How cool would that be? versus looping.
Mine is based on the line that actually travels along the southern border of Glacier National Park. I have models of historical sites along the line! Check out a video:
https://www.youtube.com/watch?v=A89olxzXCJM
You could do something over the top!!! in your space.
This is something to think about.
I strongly encourage you to check out realistic versions of models of railroads, especially your Pennsy!! :-)
You have a golden opportunity to do something great!