A funicular is a type of cable railway system that connects points along a railway track laid on a steep slope. The system is characterized by two counterbalanced carriages (also called cars or trains) permanently attached to opposite ends of a haulage cable, which is looped over a pulley at the upper end of the track. The term funicular derives from the Latin word funiculus, the diminutive of funis, meaning 'rope'.

The Metro Alpin is an underground funicular situated above the Swiss town of Saas Fee, in the canton of Valais. Opened in 1984, it links the Felskinn cable car station (2,980 meters) on the shore of the Fee Glacier to the Mittelallalin (3,456 meters) on the north flank of the Allalinhorn. The Felskinn–Mittelallalin Tunnel has a length of 1,749 meters, with an altitude difference of 476 meters between the two stations.

The Metro Alpin is the highest funicular in the world. Being a fully underground railway, it is also considered the highest subway in the world.

According to Wikipedia