Venice to Interlaken in early October

A couple of the scenic train routes from Venice to interlaaken/Berner Oberland include Venice to Innsbruck via the Brenner Pass ( taking from 5 hrs) and continuing from Innsbruck to Interlaaken/Berner Oberland ( from 6 hrs). Another very scenic route is the route over the Bernina Pass This route is Venice to Tirano, Italy ( from 6 hrs) and then Tirano to Interlaaken ( from 7 hrs).

This route through the Bernina Pass is repeatedly on “Top 10” lists of the most scenic train rides in the world, and the train route itself is a listed UNESCO World Heritage Site.

Obviously, you would want to overnight en route for either of these journeys. The most optimal choices are overnighting in Innsbruck, Austria for the Brenner Pass route and Alp Grum or Pontresina Switzerland for the Bernina Pass route. They are both in the Alps whereas Tirano, Italy is a border town with not much character or reason to recommend it.

I would highly recommend staying in the Berner Oberland mountains above Interlaaken in locations such as Lauterbrunnen, Murren or Wengen because they’re only about 30-45 minutes further than Interlaaken and place you among the most beautiful locations in the entire Swiss Alps.

Interlaaken is basically a transit junction and service center for the region and not particularly scenic itself.
Your train to Paris will depart from Interlaaken.

You can get a basic overview of train schedules at www.TheTrainline.com You can buy train tickets directly from the train companies websites. A Flexible Swiss Travel Pass likely will save you money on train fares in Switzerland.

Have a great trip!

We did that trip in reverse. Drive from Stechelberg to Chur (via Luzern for lunch and side trip to Liechtenstein). Overnight Chur. Bernina Express to Tiranno. Trenord regional train to Milan. Trenitalia fast train to Venice.

As noted, this requires an overnight in Chur, which was very pleasant. Bernina Express was the best train ride I've ever been on. Some like the regional trains that run the same route, but I figure the splurge was worth it.

trainline for schedules? No, THE site is www.bahn.com but www.sbb.ch is probaly best here if tickets are also needed

This journey is around 7 - 8 hours or more by fastest options even without thinking about scenery (and the fastest avoids a lot of good the scenery in huge tunnels). And by October the evenings will be getting darker, the 11:48 departure from Venice via fastest route is the last to put you in Interlaken before sunset, that is a very fast connection but also one which uses a long tunnel instead of the old scenic route.

Use the SBB link, make the Venezia to Interlaken enquiry for your date. What it shows will be fastest and probably via Milano and Spiez. Once an equiry has ben made it will add a Price Display, make sure that is set to FULL FARE because you presumably haven't got a Half Fare Card. Then in the settings tab switch "Via" on. This alllows you to set a different route, in that enter Kandersteg. Then run the enquiry again. This time it will show the fastest options that goes via Kandersteg, thus getting the best of the scenery and missing out the modern tunnel, you will need to change train additionally at Brig. In this case the 11:48 will only get you to Spiez before sunset but it's close enough. The 10:48 is also viable for the Kandersteg routing. Always make sure the Price Display does not say "Half Fare", any prices with a % symbol are discounted, usually not flexible and will go up. But some discounted fares for October may not have been released yet.

What to see? Nobody really goes to Interlaken to see Interlaken itself, it's the surrounding mountains and lakes that are the draw. Check which station is closest to your hotel, trains from Speiz call at both.

Interlaken to Paris is easy, Depart around 10:00, one change at Basel, arrive Paris GdL at 15:55