Way back when, in the early 50s when I got my first electric train, I “really needed” a tunnel - quite logical on a Swiss railway. What I got was one of those preformed green and brown blobs to straddle the track - but I soon progressed to silhouette mountains fashioned from corrugated cardboard. On the present layout (in the building stage) I need a mountain on the elvated section as a view block.
It will be the modern version of that blob from long ago, removable to pack it away during the winter.