4 days 3 nights in Switzerland

Unfortunately, with only 3 nights to visit 3 Swiss areas, you'll see most of Switzerland from the train window. There are late evening trains to maximize your daylight hours but few overnight trains.

That being said, I would suggest 1) the Paris-Est/Bern run with one train change in Basel Switzerland or the Paris-Gare-de-Lyon/Bern run with one train change in Geneva. There are a couple during the day. These runs take between 4.5hrs-5.5hrs. Other runs from Paris-Est and Paris-Gare-de-Lyon have more train changes and take longer. 2) Luzern/Bern. This is a 90 minute train ride and usually with one train change. If you plan well, there are a couple of runs with no train changes.

3) Luzern/Interlaken Ost. There's a 7:55 train out of Luzern with no train changes. The trip takes 2.5hrs. I think that there is a Golden Pass train on these tracks as well. From Interlaken, take the 20-min Jungfraubahn train into Lauterbrunnen. You can stay there or in Wengen or Muerren. All great. 4) Lauterbrunnen/Venice-Santa Lucia. This run will take you 8.5hrs. and require 3-4 train changes.

In my opinion, the top of the Jungfrau is a great mountain top to visit. Note, however, that it's 2hrs up and 2hrs back. The cost is $180 round-trip without some kind of Swiss Pass.

Olivia,
I would stay in the Berner Oberland area because their is so much to see and do. I loved the Schilthorn and the jungfrau trip. I bought a swiss flexi pass and it saved me a lot on the rail trips and high lift passes. We did a day trip to Montreaux and took the Chocolate train. It was fun and part of the cost was covered by the swiss pass.

I would stay in the Berner Oberland area because there is so much to see and do. I loved the Schilthorn and the JUNGFRAU trip. I bought a Swiss flex pass and it saved me a lot on the rail trips and high lift passes.

Agree again 100%. Maybe try Lucerne also? Sit and watch the stream traverse through the town and have a cold one. Or two. You'll love this area. The scenery is absolutely beautiful.

Hello Olivia. 3 nights is a small amount of time. Many people enjoyed staying at Lucern 3 nights. In one day they were on a boat on Lake Lucern (one hour, or two hours) and they walked through the city Lucern (one of the best cities in Europe, but it does not have great museums). And one day they went to the top of one of the mountains : Mt. Pilatus, or Mt. Titlis. I think the top of Mt. Pilatus has a better view. But being at the top of Mt. Titlis is a high mountain experience ! The trip from Lucern to the base of Mt. Titlis is scenic -- through a lush valley. Some people think that valley has beauty that is equal to the beauty of the Lauterbrunnen valley. Read about Engelberg and Mt. Titlis in the travel guide book "The ROUGH GUIDE to SWITZERLAND". An advantage of going to one of those mountain peaks, not to the Berner Oberland, is that you could have overnight accomodation at one place for three nights : Lucern. You could go to the top of a mountain, and ride on a boat on a big lake (Lake Lucern) and visit the city Lucern. If you would be at Lauterbrunnen two nights, and Lucern one night, you would use half a day travelling from Lauterbrunnen to Lucern, thus you could be in Lucern only one afternoon. For your train trip to Venice, I think you would want to depart from Lucern.