<<"Hi Mr Lucas, thanks again. I have decided to stay at luzern and lauterbrunnen for 3 nights each.
Is it worth taking a train from luzern to lungern and back.">>
I can see from the thread that no 0ne linked you to two essential sites for trip planning:
First- a map-
This map will let you see the geographic relationships between cities. I have zoomed it in a bit so that you can see Luzerne and Interlaken. Zoom in a few steps further and you will see Lauterbrunnen south of Interlaken.. Zoom in one or two more and you will see the train lines.
At that zoom level, pan the map, or else zoom out and focus on the region between Luzern and Interlaken, near Giswil, then pan in again. You will see the rail lines and Lungern if you go in far enough.
Since you plan to stay in Lauterbrunnen and Luzern, you will likely take the most scenic, and, unusually, in this case, the fastest route between the two. You can see that it will pass through Lungern. The trains run once per hour. If you don't have luggage with you to burden you, you could get off, walk down the hill to the lake and back up again, and probably be able to catch the next train.
I checked the SBB web site for Lungern station, and sought "Equipment and Services" at the station. The listing is empty. That means, I believe, that it is an unmanned station, which is consistent with my somewhat older memory. That means that you cannot leave luggage there while you walk. It is a bit of a walk down and back, and although pleasant, does not justify the stop in my o[pinion. The best views of the lake with the Alps beyond come from the northern end, which is about 2 km from the station. It would take you more than an hour to do the round trip on foot, unless you are very fast walkers, uphill and down.
The train goes right past that viewpoint, so sit on the right if you are coming from Luzern.
Ralroad station "Kaiserstuhl" is visible if you zoom in at the northern end of the lake. You can aaslo see thatthere is an inn/restaurant. Mouse over the station icon, and you get an abbreviated near term train schedule.
How can you find out how long it would take to get there, and when and whether the trains stop at Kaiserstuhl?
Check the timetable, which is the other essential web site for planning:
Enter Luzern as a Start, Interlaken as destination, and your time and date. If your date next year is not yet available, use any date this year, and you will see a journey once per hour. Click on a journey, and then expand the section of the route that is displayed by clicking on the "+"
You will see Kaiserstuhl is a regular stop, approximately 40 minutes from Luzern.
If you check a date in the near future, you will see that one other section of the route has no trains. Track work. A bus will be substituted for that section.
Or, if you do not wish to see the whole route to get perspective, use "Lungern" or "Kaiserstuhl" as a destination in the timetable.
Glacier Express -
Regarding the Glacier Express, check this link in detail, including the description of the route(s) and some "one-day trips" listed.
then check it out on the map I linked above ( Mapsearch.ch) and the timetable. It would not be easy to fit the entire Glacier Express in one day from Luzern. You could travel a nice part of it from Luzern to Brig to Interlaken on a roundabout route on your transit day. Go via Andermatt and Brig, and, if you have time use the old scenic upper route from Brig to Interlaken via Kanderstseg.