It is definitely doable in a day.
Note that part of the Domodossola - Milan railway is closed from 9th June to 8th September for works. Rail replacement buses will run but timetables haven't been published yet AFAIK. Expect the journey to take about an hour longer than usual.
There are alternatives if you want to avoid the buses.
Option 1 (Centovalli) :
- Florence - Milan high-speed train
- Milan - Locarno hourly RE
- Locarno - Domodossola cute little train
- Domodossola - (Brig -) Spiez
- Spiez - Interlaken Ost - Lauterbrunnen
Option 2 (Gotthard) :
- Milan - Lugano hourly RE
- Lugano - Lucerne - Interlaken Ost - Lauterbrunnen
Both are pretty scenic routes, fully reservation-free after Milan so you can decide on the day. You may use the SBB app for planning but check back closer to travel date too.
Questions welcome.
Amazing! Thanks for the detailed response. Very, very helpful
Hi thibcabe!
just wondering does the global pass cover those routes you mentioned? Centovalli and Gotthard?
Yes 100% included. The only reservation required will be from Florence to Milan (13€).