Seeing the Dolomites?

The Dolomites are not a place to do a day trip! Either extend your trip to include several more days or plan a trip to the Dolomites. Stay in Ortisei at Hotel Grones, a wonderful experience!

If you're spending three weeks in Switzerland and Italy - then add the Dolomites in somewhere. A day trip from Venice isn't doable. The Dolomites aren't in a 'town' as your post suggests. Will you have a car?

Where are you going in Switzerland? I looked at your other threads, so wondering what the final itinerary is.
The Swiss Alps are so fantastic, perhaps stay longer in the Alps. No one is ever ready to leave. Safe travels!

It’s really not feasible as a day trip. There is no train that will get you all the way into the mountains. You could get to Bolzano, then spend another hour on the bus to Ortesei.

There is a bus from Venice to Cortina d’Amprezzo, but it takes about 2.5 hrs and arrives in the late afternoon. You would have to spend the night and return the next day.

Or you can rent a car from Venice and do your own day trip.

I really appreciate everyone’s input.
So far, our itinerary is as follows (we will NOT have a car):

September 6 - arrive early morning in Zurich, freshen up and train to Wengen for 6 nights
September 12 - Train to Chur for 1 night
September 13 - Bernina Express (tickets purchased) to Tirano and stay the night
September 14-22 ?????? Undecided
September 22 - check into our reserved hotel in Venice
September 26 - check out and go to hotel near Marco Polo airport for the night
September 27 - fly back to our home
We have flight tickets, Wengen Airbnb reservations, hotels in Chur and Tirano, Bernina Express reservations and our hotels in Venice. I also bought a Swiss Half Card Pass. The rest is up in the air.

Originally, we were wanting to go from Tirano to Ortesei for 5ish nights. Then to Lake Garda for 3 nights and on to Venice. The train from Tirano to Ortesei is 8+ hours. I had no idea it would be that long. Now I’m in a bit of a quandary.
I sure could use some help from y’all. Thoughts?
Thanks!

Tirano isn't that far from Varenna, Lake Como. I know the tracks are closed now because of a landslide, but hopefully will be open by fall. Lake Como is so beautiful and serene , we just returned from our second visit, and will come back again. Safe travels!

We did do a day trip to the Dolomites from Venice, a few years ago.
It was a tour, with Viator, and we went on a minibus , about 10 people on the tour, with a very good young man as a guide.
I know we stopped in Cortina, but I don’t remember the names of the other places we stopped at.
It didn’t feel rushed, and we had lots of time in each stop to walk about and look at the scenery.
It was better than no trip to the Dolomites, and just gave us a little taste.

You will be arriving in Zurich the day after we are, though we're leaving right away for Milan via the Chur/St Moritz/Tirano route on regional trains. Fortunately for you (though not for us), the Tirano-Sondrio track maintenance closure from June 11th to September 10th should be complete by the time you need to use it, meaning you'd be able to grab a direct train from Tirano to Varenna (Lake Como) or Milano if you'd be interested in either place.

If you really want to go spend time in the beautiful Dolomites during your as-yet-unplanned days, I have a suggestion: go directly from Tirano to Bolzano via rental car (3.5 hours). I know you were not plan on renting a car, and I get that it's an extra thing to deal with. But having a car in the Dolomites and Lake Garda is an excellent way to see each of those areas, based on what I've read in this forum. You could pick up in Tirano and drop off at the Venice airport or train station. Something to consider.

I would agree to see the Dolomites after Tirano. You have plenty of open days for a visit. Check out the Val Gardena.