SNCF's Yellow Train (Le Train Jaune) Part 1 Villefranche de Conflent 

This meter gauge 850V DC third rail train climbs from Villefranche de Conflent 1165 meters on gradients up to 6%. It crosses several viaducts and passes through numerous tunnels while climbing up several steep gorges. From the summit It descends to an Alpine plateau and its terminus at La Tour de Carol close to the Spanish border. Here three different gauged railways meet (meter gauge, French standard gauge and Spanish Iberian gauge [1668mm]).
See also Parts 2 & 3 for the ride to Latour de Carol and return.