Opened in 1912, the Karwendelbahn railway was Austria’s first fully electrified railway. The line stretches from Mittenwald to Innsbruck. Over a distance of 32.1 km, the train leads through 16 tunnels and over 18 high bridges and viaducts. In March 1910, the first cut was made into the legendary Martinswand rock face. The Martinswand, which rises sheer and craggy from the Inn Valley, and the rugged rocks of the Schlossbachgraben posed the greatest challenges.
At a height of around 60 m above the water table, the line negotiates the Schlossbach stream by means of a 66 metre-long arched, iron-girder bridge. The Finstertal viaduct was built on the barren slopes of the Hechenberg mountain; hanging viaducts were constructed over the Schlossbachgraben gorge and the Kaiserstand viaduct stands beneath the ruins of Fragenstein castle. The Gurgelbach viaduct was constructed near the village of Reith bei Seefeld, and the Isar bridge near Scharnitz.