It links Lake Geneva to Lake Lucerne via Interlaken. There are also direct connections to both Geneva and Zurich airports if needed.
The line is split into three sections. The line from Montreux to Zweisimmen is operated by MOB. From Zweisimmen to Interlaken it is run by BLS. The GoldenPass Line from Interlaken to Luzern is operated by Zentralbahn.
This is a very scenic voyage and photographs will be eventually added.
You can read more about this line at the official website here: GoldenPass Line.