walking the Bern-Lötschberg-Simplon line

Ausserberg on the Sudrampe. (Kurt Zwahlen pic)

No, this major railway has not been turned into a rail trail, but there are walking tracks that accompany it with varying degrees of proximity.  You can't walk through the railway tunnels, but you can walk over the top of them.  And like most of Switzerland, the experience is very scenic, which helps compensate for the general drain the country makes on your wallet.  

This 182 page book is produced as a guide for walkers of what is to be seen on the Wanderweg, and divides the north and south ramps (Nordrampe / Südrampe) into 10 stages for the approximately 60 km (railway) distance between Frutigen on the North Ramp and Brig at the end of the South Ramp. The book is available in both German and French editions.