Constructed in 1940 by the Swiss military to supply troops guarding the nearby Austrian border. The ‘Alplibahn’ rises from 600m to 1801m, is 3485m long, and takes 14 minutes each way.
It is preserved and run (including the very reasonably-priced mountain restaurant) by unpaid volunteers.
Details and reservations at http://www.aelplibahn.ch or firstname.lastname@example.org
Worth a day to enjoy the views and walk on well-marked trails at 1800m.