So day trips to take the Glacier Express or Bernina Express are impossible. But don't worry there are other very scenic journeys !

(Btw the Glacier Express require a 49 CHF seat reservation and Bernina Express 26 CHF but there are hourly reservation-free regional trains on the same route).

What is your entry and exit point ? If you're coming from Lake Como for example, you could take the Bernina route along the way.

Day trip ideas :

Option 1 :

- Geneva - Montreux - Zweisimmen - Spiez - Interlaken (Golden Pass route)

- boat on either Lake Thun or Brienz (included)

- back via Bern (faster)

Option 2 :

- Geneva - Lucerne

- Lucerne - Interlaken Ost

- Interlaken Ost - Bern

- Bern - Geneva

Option 3 :

- Zermatt (but train to Gornergrat is not included, 126 CHF for adults, 30 CHF for children)

Option 4 :

- Leysin, Les Diablerets or St-Cergue - La Cure : scenic routes, not too far away…

Option 5 : boats on Lake Geneva (50% discount)

Unfortunately Geneva is pretty much the worst place to explore Switzerland, being so far away from the rest…

But you could go to France, for example Annecy (direct train) or Chamonix/Mont-Blanc :

- Geneva - Martigny - Vallorcine - Chamonix

- Chamonix - St-Gervais - Geneva

More info : https://www.interrail.eu/en/plan-your-trip/tips-and-tricks/trains-europe/railway-companies/swiss-railway-companies-discounted

There's also a map available which include all railways where it is valid. But I can't find it...

Here's the map with the validity of Interrail in Switzerland: https://www.interrail.eu/content/dam/miscellaneous/Map%20of%20Switzerland_SBB.JPG

Thanks to your initial direction (& patience), I am able to grasp the locations (a bit) & improve/crystallize my plan. Really appreciate that & would require a bit more of your time/guidance.

So I am trying to change my plan a bit (within my budget), to take Bernina, Glacier (& maybe Golden Pass). So I am planning that I move from Geneva (on the last day) and spend the last night in Chur. So my Accommodation plan would look like a bit of this:

• Day 1 - Arrival from Paris to Geneva (night stay)
• Day 2 - Geneva (night stay)
• Day 3 - Geneva (night stay)
• Day 4 - Geneva (night stay)
• Day 5 - Move to Chur (via Glacier Express) for Night Stay
• Day 6 - Move to Rome (via Bernina Express till Tirano), Milan and Night stay at Rome

Now, roughly my plan can look like this (but needs extreme improvement):

1st Day (Day 2 above)

- Geneva - Montreux - Zweisimmen - Spiez - Interlaken (Golden Pass route)

- boat on either Lake Thun or Brienz

- back via Bern

2nd Day (Day 3 above)

Brienzersee, Iseltwald, Grindwald, Lauterbrunnen (or something like this???)

3rd Day (Day 4 above)

?????

4th Day (Day 5 above)

Checkout from Hotel, Take Glacier Express till Chur, Check in, Lucerene, maybe visit Uri,Zurich or any other (if recommended) or something like this???

5th Day (Day 6 above)

Move to Rome via Bernina Express & other regional trains.

Now coming to a few miscellaneous points:

1. I have Eurail Global Pass and what I have read about it is (regarding Switzerland) that 90% of regional and special trains like Bernina, Golden Pass, and Glacier Express are totally FREE (regular compartments) with no reservations required. However, you mentioned few charges with Bernina etc???
2. Your detailed feedback is required to help me fill in the travel itinerary.
3. I am not sure about timings of Galcier, Golden Pass & Bernina Express, so as to fit in my plan
4. Any other suggestions are most welcome.
5. Due to my stay of 4 x nights in Geneva, I will have to travel a lot. I understand it, but I am ready to do so, as visiting Switzerland again soon is not possible. So want to make full use of this opportunity.

You can't travel on the Glacier Express without paying the 49 CHF, however you can take the hourly regional trains on the same route for free. Actually they're even better as they're less crowded and have pull-down windows :)

Bernina Express : there are reservation-free carriages at the front or hourly regional trains.

Here is a suggestion which includes visiting most of the country. Please don't travel 10h every day, you won't enjoy it.

DAY 1 (or 2 or 3, no order)

- Geneva - Montreux - Zweisimmen - Spiez - Interlaken Ost

- boat to Brienz

- train to Lucerne and then back to Geneva (direct or via Olten)

You'll get a very good overview of the Interlaken area whilst not spending a lot of money (Grindelwald and Lauterbrunnen are not included on Eurail, only 25% discount).

DAY 2

- Geneva - Zurich - Rhine Falls & Stein am Rhein (maybe)

DAY 3

- Chamonix round-trip as explained above (a bit less travel time than usual)

DAY 4 (full Glacier Express route)

- Geneva - Brig - Andermatt - Disentis/Mustér - Chur. Stop along the way, trains run hourly

DAY 5 (full Bernina Express route)

- Chur - Tirano - Sondrio (bus due to engineering works) - Milan - Rome

Bernina Express and Glacier Express need a seat reservation. And this has a cost. 

Glacier Express between 29 and 49 CHF.

Bernina Express between 20 and 26 CHF.

But you can avoid this, using on the same route local trains that run hourly. No reservation needed and less crouded and on top you can exit the train and take the next one.

On Glacier Express route no direct train except the Express, local trains need to change trains. For timetables look at sbb.ch and put via Andermatt. If you don't put the via you will get trains via Zürich.

Same on Bernina route, local trains on the same route or you use one of the carriages on the top of the Bernina Express. This caeriages has no panoramic windows but can be open. 

Schedule example :

- Bernina Express Chur - Tirano 08:28 - 12:49 (reservation-free carriages at the front)

The connection to the 12:56 bus to Sondrio is too tight. Instead eat lunch and make a break there.

- Bus Tirano - Sondrio 14:56 - 15:36 (pass valid)

- R Sondrio - Milano Centrale 15:41 - 17:40

- FR Milano Centrale - Roma Termini 18:00 - 21:10 (or a later one) 13€

Thank you for the detailed guidance. I am still finalizing my plan & with your help, I have been able to get a lot of clarity. Would require a bit more of your time. Thank you for your patience.

So based on your suggestion (& my budget), I have given up the idea of riding the Bernina, Glacier, or Golden Pass. And now my complete plan in Switzerland revolves around fully utilizing the Regional Trains.

In a Nutshell, I plan to generally follow the train routes of Bernina, Glacier, and Golden Pass, using the hourly regional trains. Will get off at different locations in between and then ride the next train for further travel. As you suggested, will also try to reduce my ‘train’ times to a minimum, once I further grasp the orientation/information, however, for now, I am just analyzing the plan in full to decide what to miss & to make it crisp.

So generally I will follow the following day-wise routes (may divide them over days & are not in a specific order):

Day 1 (Glacier Express Route covered using regional trains)

Geneva-Zermatt-Brig-Andermatt-Muster-Chur-Tiefercast-Filisur-St Mortiz

• I could not find the end (red) part of the route above on the Rail Planner App, if I want to go to St Mortiz, which train to use?
• By putting Geneva-Chur in Rail Planner App, I am getting Geneva-Zurich-Chur Route. I tried doing what @Angelo suggested above: “For timetables look at sbb.ch and put via Andermatt. If you don't put the via you will get trains via Zürich.” But the website is giving me some error regarding ‘Under Maintenance’, so I will try later to find out the results it gives... However, based on the results that come, I simply ride those trains manually upon reaching the relevant train station?
• What are some good places to get off on this route?
• Any other suggestions?

Day 2 (Golden Pass Route covered using regional trains)

Geneva-Lausanne-Montreux-Gstaad-Zweismmen-Interlaken-Lucerne-Zurich-Bern-Geneva

• For this route as well, I find the manual route/trains using sbb.ch and then ride those trains manually upon reaching the relevant train station?
• What are some good places to get off on this route?
• Which train to use to reach Grindwald, Lauterbrunnen?
• Any other suggestions?

Day 3 (Bernina Express Route covered using regional trains)

Chur-Reichenau-Thusis-Filisur-Pontresina-Tirano (or even back to Geneva, if possible?)

• Is this route doable using regional trains? To what extent or place?
• For this route as well, I find the manual route/trains using sbb.ch and then ride those trains manually upon reaching the relevant train station?
• What are some good places to get off on this route?
• Any other suggestions?

Lastly, in case I go to Rome from Geneva (as per my original plan), the Rail Planner is giving me the following routes/trains:

Geneva-Olten-Milano Cetrale-Roma

• So even if I follow this plan, is there an alternate (scenic) route available to even enjoy/explore more during my train to Rome?
• The train from Olten to Milano Centrale is also asking 13 Euros in addition to Milano Centrale-Roma (15 Euros)…??

Thank you once again for your patience & support!

I'd travel to Chur (or St. Moritz but it is way more expensive), stop for a night there and the next day go to Rome. You'll save hours of transportation.

Yes the direct EC to Italy requires a 10€ seat reservation but it can be avoided by taking a regional train from either Lugano (not longer at all) or Domodossola (a bit longer). The route via Domodossola isn't shown on Rail Planner due to a bug but SBB will give you the correct times. But please go to Chur and then Rome, you'll save a lot of time.

For planning use SBB app/sbb.ch : search legs separately or add multiple "via". The fastest route is via Zurich so that's what will show (but you miss the best scenery then). Rail Planner : you need to enter the correct names or it doesn't work -> Tiefencastel, St. Moritz

Regional trains are as good as the panorama carriages, if not better : less crowded, pull-down windows and you can stop along the way if you feel like it !

Interlaken Ost - Grindelwald/Lauterbrunnen : direct trains. You go to the ticket counter there to get tickets with the 25% discount.

Thank you so much!

While selecting the route from Lugano, it gives a default route from Geneva-Zurich-Lugano. I was just wondering:

1. If I can find an alternate (direct) route from Geneva-Lugano (from the South) without going to Zurich?
2. If I follow the route from Zurich-Lugano, is it possible to (almost) follow the route of Bernina Express in regional trains?
3. Is there a way to select a route on regional trains, that passes by Lake Como & Varenna?

Please have a look at a map. The Glacier Express runs from Zermatt and Brig to Chur and St. Moritz. The Bernina Express runs between Chur, Samedan (near St. Moritz) and Tirano.

Geneva - Zurich - Lugano is the fastest route : 4h43 total. An alternative route (taking part of the Glacier Express route) is :

- Geneva - Brig - Andermatt - Göschenen - Bellinzona - Lugano : about 7h (+ 5h to Rome).

If you'd like to take the Bernina route and on the same day go to Rome, the route would look like this :

- Geneva - Zurich - Chur - Samedan - Pontresina Tirano - Milan - Rome (15h30 total by leaving at 05:42)

If you'd like to travel along both the Glacier Express and the Bernina railways, you have to spend a night in or around Chur (what I'd do).

- DAY 1 : Geneva - Brig - Andermatt - Disentis/Mustér - Chur (7h33)

- DAY 2 : Chur - Samedan - Pontresina - Tirano - Milan - Rome (about 12h)

Planners will explain everything.

EDIT : To answer your last question -> if you take the Bernina Railway, you'll then travel along Lake Como to Milan (but there are loads of tunnels)