Flying into Milan then off to Varenna

You mean in Milan? Go see the Duomo at least.

While in Varenna ride the ferry to all the different places on the lake. Also walk along the waterfront in Varenna.

Looks like Duomo is a distance

No you can't walk. You take the metro it is easy but if you got suitcases

Suitcases are not a problem. There is a "left luggage" at the Milan Central Train Station.

Backpacks for the win!
Is it a lot of time from airport to Duomo then back to train station?

The train from the airport to Milano Centrale rail station is about an hour itself. You pretty much have to go to Centrale whether you go on to Varenna or hang around Milan.

The airport train takes about 45 minutes to an hour. Then the metro to the Duomo is 15 minutes more or less

I am perplexed by this question, sounds like you want to be talked into seeing something in Milan. I am trying to guess at your circumstances. (Maybe starting a RS tour at 5 pm the day you fly into Milan and are wondering if you can fit something in before your tour?) I suggest you spend just 30 minutes looking at the Milan page on this website or google Milan and take a peek. If you don't see anything you can live without seeing skip it and go to Varenna.
I am spending 22 hours in Milan and had to cut my list in half in order to fit for time.
Here is my list:

1. See the Milan Cathedral including inside and the roof
2. Eat a panzerotti at Luini's
3. Convent of Santa Maria delle Grazie to see da Vinci's The Last Supper (requires booking 2 months ahead)
4. Sforza Castle to see Michelangelo's Rondanini pieta
5. Eat ossobuco e risotto alla milanese
6. Have tea at The Crazy Cat Cafe
7. If time walk through Galleria Vittorio Emanuele II

It is only 1.7 miles from Milano Centrale train station to the duomo. Surely that isn't too far to go after how many miles from home to Milan? But I still say if it doesn't inspire you, skip it.

I was at the Duomo in July. I doubt your backpack of whatever size will be allowed anywhere. There is heavy security both for going inside and for going up top. There may be places to leave it, but I didn't notice any. Best to leave it at Milano Centrale.

Here's a basic link to Duomo visiting information. Here's the quote from it.

"In order to facilitate the supervision of the Public Security Authorities to access to the Cathedral, you are invited to empty the pockets of metal objects and open the bags . We also inform you that it’s forbidden to enter the Cathedral with helmets, glass objects and luggage. We strongly encourages you not bring big bags."

I got Duomo Pass A. Access to the roof is outside the Cathedral with it's own separate security. The elevator is tiny. I think it held about 9 people including the operator. There are steps up to it, and more up top, but going up there is one of the most enjoyable things I've ever done on a trip to Europe. For me it wasn't about the view. It was about the architecture.

Cindy,

Are you arriving in Milan from a long international flight and then planning to sightsee all day prior to going to Varenna? If so that could be a gruelling day!

As the others have mentioned, you won't be able to take luggage into the Duomo or other sights so you'll have to stash it at the Deposito Bagagli at the station. Allow lots of time for that as it can take awhile if there's a queue.

The Metro ride from Centrale to the Duomo doesn't take long but of course there's also waiting time, buying tickets, etc.

That's not something I'd attempt after a long flight but YMMV.

Yes flying from New York....kind of why I was checking if it is really worth it for us to try and do anything in Milan. Think it’s best just to head to Varenna.

cindy,

Are you flying in to join a RS tour? If so, my suggestion would be to head straight for Varenna, check into your hotel and perhaps have a short rest before the meeting.

Although you flight is supposed to arrive at 08:30, there could be delays. If several other flights arrive at the same time, Passport control may be a bit busy and it could be 10:00 or later before you get into Milan. The train to Varenna is another 1H:03M.

Are you clear on the trains to use from MXP to Varenna? If you need more information on that, post another note here.

Since you are flying into Milan, consider going straight on to Varenna. It is a great place to refresh, get over jet lag, and acclimate. If you are joining a tour, consider going over a day (or two) before it starts. Not only will you be well rested to start the tour, you'll also have some time built in to handle flight delays and such.