Coming from Rome for 6days in Switzerland

Hello mondtan and welcome to the forum. As for your questions: staying in Interlaken, Bern and Lucerne would be fine. Bern is especially suitable for city tours, as it isn't located within or very close to the Alps (whereas Interlaken and Lucerne are). A train ride from Bern to Spiez, which will get you to several mountain destinations, takes only half an hour though, so Bern is still quite a central location. If you want to spend as much time in the Alps as possible, you may want to consider an overnight stay in the southern part of Switzerland as well (such as Zermatt or Saas-Fee) and/or spend the extra day in Interlaken instead of Bern. But again, it depends on what your preferences are. If you like staying in larger towns/small cities, the itinerary you mentioned is absolutely perfect.

There are two main routes by which you can enter Switzerland from Italy. One runs through Chiasso, Lucerne and Meiringen; the other one through Domodossola, Brig and Spiez (this is the most direct one). Train journeys (including trips starting in Italy and ending up in Switzerland) can be planned through the Swiss timetable. Depending on your connection, the validity of the Swiss Pass starts at either Chiasso or Domodossola. So up to Chiasso/Domodossola, you'll have to pay full fares. From there on, your inward journey will be for free with a Swiss Pass. So you''ll have to purchase a regular ticket up to Domodossola/Chiasso, and continue your journey for free from there on with your Swiss Pass, in either another train or in the same train. For international trains, you will have to make seat reservations. This can be arranged for online, which you may want to combine with the purchase of your Swiss Pass.

A map showing the exact area of validity is available through the link 'Overview of the network on which the Swiss Pass is valid' at the Swiss Pass page. Almost all regular train, bus and boat routes are covered by the Swiss Pass. Only mountain transportation requires the purchase of additional discounted tickets.

I hope this provides some answers. Good luck on planning your trip, and have a wonderful honeymoon!

Sorry Annika, some questions about bookings with Swiss passes.
I just tried booking on the website for Domodossola to Interlaken, and it goes straight to the option of either Full fare or Half fare, without an option for GA. Is it because this particular route doesn't take reservation (no R indicated on comments)? In that case, do we just go to Domodossola station directly and board with the Swiss pass, without any tickets?
Also, I noticed that Brig to Spiez allows reservation, but putting in that query also doesn't give an option for GA.
Lastly, I tried Grindelward to Jungfraujoch, which should be 25% of the fare with Swiss pass, and again there isn't such an option.

Am I doing something wrongly? Or is SBB not the site which I should be booking tickets on? I do notice that the GA option appears when I am trying to book a cross border route from Italy, but not when trying to book routes within Switzerland. Please advise. Thank you.

Best regards,
Dazmond

Hello Dazmond. Don't mind asking your questions! The SBB site is the one I referred to (so you're trying at the right website), but the procedure I described is suitable for ordering international train tickets and seat reservations. That's why I pointed this out for booking your trip from Rome to Interlaken. You can pick a 'GA' option (equal to the Swiss pass discounts) for international trips, so that the booking system can charge you for the foreign (in your case, the Italian) leg of the journey, but not for the Swiss leg.

For trips within Switzerland for which seat reservation isn't required, or even is impossible, it makes sense that you can't choose the GA option. Making the trip with a GA/Swiss Pass means, after all, that the entire trip is for free, and apart from that you can't even make seat reservations - so nothing would be left to order. Seat reservation isn't possible for the trip from Domodossola to Interlaken, and the entire trip is for free with your Swiss Pass, so there's no need (and no possibility) to order a seat reservation for this trip in advance.

The SBB system only offers either regular full prices or half fare prices. As the Swiss Pass offers a different discount (25% instead of 50%) for the Jungfraujoch trip, you can't pick the right fare when ordering your ticket in advance. If you wish, you can order your seat reservation for the Jungfraujoch trip through the Jungfrau Railways website. You may also be able to purchase your ticket through the webshop there, but currently there's error on the page, so I can't check. It may be wise though to reconsider purchasing this ticket in advance. It's an expensive trip, and if weather is bad at the day for which you reserved seats and ordered your tickets, it may be a waste of your money. The tickets can easily be bought at a railway station (such as Interlaken or Grindelwald) before boarding the train, with the appropiate Swiss Pass discounts. A local purchase would allow you to make sure that weather is fine before leaving.

As far as I know, the SBB website doesn't allow you to make seat reservations only, without ordering (discounted) tickets for the same trip. This would explain why you can't choose the GA option for the Brig - Spiez leg. If you definitely want to arrange for seat reservations for this part of your journey (although they're not required and most of the times not really necessary), you could contact the SBB and ask for information.

I hope it's clear now!