train to Venice

If u want to go up to jungfrau (少女峰), u have to go to interlaken first. It is quite far from geneva (around 2hrs), closer to luzern (1hr)

If u want to go to these 3 places, i recommend the plan below:
day1: geneva
day2: luzern, after luzern, go directly to interlaken and stay in accommodation in grindelwald or lauterbrunnen which between jungrau and interlaken.
day3: go up jungfrau in the early morning and come down around noon. u can go to lauterbrunnen which has a amazing waterfall inside the mountain. or go to thun/bern
and then go to italy at night

***actually interlaken is between geneva and luzern, i put interlaken at the end becasue it is faster for u to go to italy.

from interlaken to italy, the fastest way take around 8-9hrs. i recommend night train :interlaken - spiez - bologna - venice.

if u go to the capital of switzerland, bern after interlaken, u can travel there in the afternoon. and then take the direct nighttrain from bern to bologna and then change to venice. (actually the train from bern to bologna is same at the one from spiez)

if u go from luzern, u also have to go to bern to change (with less transition)

u can check the schedule of the train in the following web site of swiss railway.
http://fahrplan.sbb.ch/bin/query.exe/en?

hope it help

There is 3-hour train distance bewteen Geneve and Luzern.
From Luzern to Venice, there is no direct train service, you have to change in some cities.
If you want to take the night train, you may need to change 2 times in Berne and also Bologna. The journey will be around 11 hours
If you want to take the day train, you may need to change 1 time in Milan. The journey will be around 7 hours