Not as dramatic as the others but I like the down run on the Southeastern mainline from London and the way the tunnels divide the scenery. London to Elmstead Woods tunnel you have terraced houses, flats, council estates, once through the tunnel you find yourself in leafy suburbia through Chislehurst, Petts Wood, Orpington and Chelsfield. After the short Chelsfield tunnel, deep cutting of Knockholt and the longer Polhill tunnel you suddenly find yourself in a different world - classic Kentish scenery, oasthouses, farmland etc. I love bursting out of Polhill tunnel on a sunny day. It's not the west highland line but there is something very ordered and pleasing about it.