Route 125 in central PA is a great north-south route that crosses a number of mountains and is pretty twisty, as a result.
A few sections are straight going through the valleys between the mountains. The route runs from Shamokin PA (in the north) to Pine Grove (in the south).
The twisty sections are from Shamokin to Tremont. A short section of straight road outside of Tremont gets attention from the sport bike rider doing some high speed stuff.
Be careful of gravel in corners as the road is frequented by coal carrying dump trucks, on occasion.
There are a couple of places along the route to pull over and take a picture of the surrounding area, but in many places the road is fairly narrow and pulling off the side of the road could be a problem, with a sharp drop off edge onto loose gravel.
At 24 miles of fairly twisty road (by PA standards), it’s a fun road to do in one direction, then turn around and attack it again.
As a side route/detour, head over to Centralia, where a coal mine is on fire, under the ground where a town used to stand. It has been burning for about 40 years.