Traveling from Interlaken to Jungfraujoch (the "Top of Europe") with a Swiss Travel Pass involves a specific multi-step journey that combines standard rail with specialized mountain cogwheels. From Interlaken Ost, you first take a Bernese Oberland Railway (BOB) train toward either Lauterbrunnen or Grindelwald. The Swiss Travel Pass covers this initial leg of the journey 100%. From those towns, you transition to the Wengernalp Railway (WAB). Since late 2020, the fastest route is via the Eiger Express tricable gondola from the Grindelwald Terminal, which whisks you up to the Eigergletscher station in just 15 minutes. From Eigergletscher, you board the final Jungfrau Railway cogwheel train for the tunnel ascent to the summit. It is crucial to understand that the Swiss Travel Pass does not cover the entire trip for free. While it provides free travel to Wengen or Grindelwald, it only offers a 25% discount on the final high-altitude sections (the Eiger Express or the mountain trains to the top). You will need to present your pass at a ticket window or use the SBB app to purchase the discounted "Top of Europe" ticket.