I discovered the metre-gauge RhB (Rhätische Bahn) in 1982 during an otherwise car-based trip to Switzerland.
I don't think I've been so comprehensively delighted by a couple of weeks of train travel since.
We used rover tickets (with bus and some mountain transport thrown in) to tour the wide Graübunden area, based in Pontresina.
It's a winning combination of scenery, engineering ambition, operational efficiency and popular affection.
You can even ride in the bench seating of the bright yellow open air carriages on the Bernina Express (sorry, poor picture).
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There are plenty of others, even if they don't quite reach the ambience of the RhB.
Examples are:
- observation car on the Transalpin service (Zürich-Innsbrück-Graz)
- Mediterranean coastal lines (St Raphael-Ventimiglia-Genoa, and Naples-Villa San Giovanni-Sicily, including train ferry to Messina), Cerbere-Portbou
- crossing the Oresund Bridge (Copenhagen-Malmo)
- journeying through Transylvania (RO), either on quality EC trains or the (very) local stoppers
- travelling through the Rhine, Elbe and Mosel gorges
- mountain passes/tunnels: Gotthard, Semmering, Tauern, Tende, Zamora-Orense (ES - like the Gotthard, recently bypassed by a new HSL)
- gulaschsuppe on many central European trains, pork and dumplings if they are operated by ČD