Rothorn
Brienz Rothorn Bahn
The railway from Brienz up to Rothorn offers both impressive views and the chance of getting a ride on a steam train. The short journey up to Rothorn takes an hour but given the impressive views it is well worth the time. Just make sure that it is a fairly clear day before you get started.
Brienz is located on the east side of Lake Brienz. From Interlaken (Interlaken Ost) you can take the train to Brienz (about 20 minutes) or the boat (about 80 minutes) The boat is nicer, so it is worth taking the cruise at least once.
The Brienz Rothorn railway was opened on 17 June 1892. The track is 7.6 kilometers (4.7 miles) and includes eight tunnels with a total length of 690 meters. The track is very steep so a rack system is used and the locomotives are specially designed to cope with the gradient. The steam locomotives incline sharply forwards. This The gauge is very narrow, only 800 mm. The journey between Brienz and Rothorn takes an hour.
Generally, steam trains are used, although a few diesel locomotive exist as well. Most of the steam locomotives are from the 19th century. In order to avoid overheating the boiler must be fairly level so that water covers the whole system. This is why the steam locomotives are tilted forwards. On the steep track they are more or less horizontal.

From Brienz, at 566 meters above sea level, the train climbs up the upper station, Brienzer Rothorn Station, a bit below the Rothorn summit which is 2244 meters above sea level. This makes the average gradient 22%. The Rothorn summit is another 104 meters further up, at 2350 meters above sea level.
Halfway up the mountain, at Planalp (1346 meters above sea level), the train makes a short stop. You can take photos while the staff replenish the water supply. On the way up the vegetation changes, no more trees, just grass.
The track ends a little bit below the summit so you have to walk the remaining bit up to the summit. Fortunately, it is an easy walk. On a clear day, the views are wonderful. Even if the weather is not perfect, you generally get good views of the Lake Brienz and the summits of Eiger, Mönch and Jungfrau. Note that it can be a good idea to bring a sweater or a fleece. It can be both cold and windy at Rothorn, even if it is warm down in Brienz.
If you have the time, it is possible to stay at the hotel, Hotel Rothorn Kulm, and enjoy the sunset from the top of the Rothorn. And the next day you can walk down to Brienz, it takes roughly four hours to get down to Brienz. The hotel has a restaurant, so you can just stay for lunch before taking the train back down to Brienz.
Note that the Brienz Rothorn Bahn is closed during winter and spring. Generally, it is operating from May to October.
Like most things in Switzerland, the Brienz Rothorn Bahn is not cheap but on a clear day it is well worth the money. You get a ride on a steam train and some impressive views.