The train to Jungfraujoch leaves from Kleine Scheidegg every half hour. There are two ways to get from Interlaken to Kleine Scheidegg-- via Grindlewald or via Lauterbrunnen. I went up one way and came down the other to see more.
I took the 7:22 train out of Baden changing in Bern, Interlaken, Grindlewald (!!!), and Kleine Scheidegg. Kleine Scheidegg was seriously crowded and though I was in line for the 11:00 train to Jungfraujoch, I had to wait for the 11:30-- which wasn't so bad in the end because I got a seat! I recommend being in line right as the train before the one you want to take loads.
I think L would be better off taking the 6:22 trains.
The view from Kleine Scheidegg. (First: Eiger and Monach; Second: Monach, Jungfraujoch (in the valley between the two peaks), and Jungfrau.
So Jungfraujoch is a serious tourist destination. But, its worth it because its one of the only ways to see that type of scenery without being an alpine climber. They've got it set up well, though, so it works ok with so many people. Most of the train ride up is in tunnels and actually, most of Jungfraujoch is in tunnels inside the mountain with small areas poking up as viewing areas.
First you go through some tunnels then you come to a viewing platform up on the "Sphinx"
You might not be able to tell, but those three groups of two little black dots on the ridge of this mountain (Monach, I think) are people!!!
Then you go back down through some tunnels and get to the Ice Palace. Yes. Its a cave. In a glacier. Check that off the bucket list!
Then you go through Alpine Sensations. I'm not really sure what's up with that. Its kinda creepy.
Then you go out on the snow! Yay!
At some times, I think you can actually ski and tube and stuff up there but that was closed.
So after all that you eat lunch. Bring you own lunch. Seriously. I mean the food was decent but SOO expensive. Also bring lots of water. Its $5+ for a 0.5L bottle.
After that, you're pretty much done. It might seem a bit anti-climactic but the views are so amazing and majestic it really is worth the trip. Also, all the touristy stuff is included in the train ticket so you're not paying any extra to do it.
When you're ready to go back down, get in line for the train. You probably won't make the first one that comes. Just too many people. The ride back to Kleine Scheidegg is faster than the ride up. You can get off and walk down (or you could have walked at least part of the way up... but why??) at one of the 2(?) stops along the way.
I would reccomed walking from Kleine Scheidegg though. I walked to the first station, Wegneralp, which was about 2km down the mountain. If you want, you can walk all the way to Wengen which is only 6km. I would have but I wanted to save my knees for Prague. You might want to look into this before you buy your ticket up. Might be able to save some money.
This is totally a bridge for cows to cross the train tracks!!
The way down from Wegneralp to Lauterbrunnen was beautiful!! Tons of waterfalls and alpine villages!
From Lauterbrunnen, I took an R back to Interlaken then an R to Spiez (no AC!!!!) then an EC to Bern (crowded!!), and finally the IR back to Baden. I was exhausted!!! But, it was amazing!!!
And here are some panos...