Venice

Take the vaporetto over to San Giorgio Maggiore, the little island off St. Mark's. Nice church, beautiful view from the bell tower, quiet gardens, small crowds.

Get a Chorus Pass, which covers the entry fee to about a dozen churches. You get a map when you buy the pass. Each day, pick one or two that aren't located close to Piazza San Marco or right next to the Rialto Bridge and walk to them. Don't be in a hurry, as this will allow you to wander some of the less-visited parts of Venice--just enjoy discovering different nooks and crannies of the city. The bonus--when you do arrive at whatever church you've chosen, it will have plenty of great art.

We enjoyed Scuola Grande di San Rocco

Torcello (near Burano).
San Giorgio campanile for great views over to St Marks (across the lagoon from SMS)
Santa Maria della Salute
Correr Museum (enjoyed very much)
Arsenal - there is a Naval History Museum near there
There is somewhere where you can see where gondolas are repaired or made

After 4 trips, one of my fav things to do is just wander and go into random churches.

Have you considered a side trip to Verona and / or Vicenza? Fairly short train ride and lots to see in each place. Verona has enough to keep one busy enough to stay overnight. But if you day trip get a really early start, come back in the early evening, and just make a whole day of it.

We are planning for an upcoming visit to Venice. In addition to all the great ideas posted we plan to see a Vivaldi Concert. www.interpretiveneziani.com.
If anyone has been to this venue, how far in advance would you suggest purchasing tickets? Another helpful link we found is visit-venice-italy.com.

Any chance you will be there for the Biennale? We finally hit Venice during 2017 Biennale (our 10th trip to V) and it was amazing!

Like Nicole, we also just like to wander. Years ago I picked up the book "24 Great Walks in Venice" (now out of print but often available used) and we have used it every trip to explore the hidden corners.

RE: tickets for Interpreti Veniziani. There are no reserved seats, and the few times I've been many of the people sitting around me had bought their tickets earlier the same day. I'm too much of an OCD planner for that, so bought my tickets the day before. If you want to sit up front--and it is fun to watch them perform up close, especially the lead cellist--get to the venue 45-60 minutes early and line up.

Maybe get a copy of “Secret Venice” by Jonglez. All sorts of fascinating little details in that.

Take a picnic to Certosa

Take the No 12 vap to Sant’ Erasmo and go for a walk.

Check out the Querini Stampalia Foundation.

Visit the Fortuny Museum

Visit the Tre Ochi photo gallery on Giudecca.

Picnic on Torcello.

Take the tram to Forte Marghera, tram then a 500 metre walk, for lunch. There are a couple of bars there.

If the Biennale is happening, late May to early November, you can visit the Arsenale.

Check out the Sacristy of the Church of San Polo, a brilliant Stations of the Cross by Tiepolo.

Visit the Armenian monastery on San Lazzaro if it is open for a visit. A great Tiepolo piece, newly restored, and I think they have created a printing museum there.

Take a look at the Olivetti showroom in the Piazza.

I could go on, but this might give you a few ideas ........

The gondola repair shop is near San Trovaso church; peak in the doorway or view from the other side of that small canal. Have you been to the Jewish Ghetto neighborhood and synagogues/museum? There are also smaller house/palazzo museums such as Ca Rezzonico, Palazzo Mocenigo, and Biblioteca Nazionale Marciana (near San Marco and Doge's Palace). Rick's Venice guidebook covers a few more of these places than does his big Italy book.

Rent a bike to see the flamingos in the lagoon.

http://en.venezia.net/lio-piccolo-pink-flamingos

We will only be there for three days but this would be something different that I would like to do if I had more time there

Eric, thank you for the concert information! Appreciate it.
Thanks to all who have given us more ideas!

Get reservations for Scrovengi Chapel in Padua -- glorious Giotto murals. Easy train ride from.Venice.

Take a short train ride to Treviso.
No tourists, lots of streets to wander in.
Or Chioggia: a fishing village out in the lagoon.
Vaporetto to Lido, bus along Lido, short ferry to the next island (?Pellestrina?), bus, then another ferry.
Takes a couple of hours, but interesting to see another part of the lagoon life.

San Michele has the fascinating cemetery, and as a bonus, few people seem to go there, so you can escape the crowds.

Walk down to the tip of the island in St. Elena. It's a totally different view of Venice with ZERO tourists.

Be sure to take in an opera. One company dresses in baroque clothing, with three vocalists and nine instrumentalists. They perform songs from many Italian operas and are quite sensational, even if you are not an opera fan

Scuola Dalmata di San Giorgio degli Schiavoni, best Carpaccio including St. George & the dragon, Take binoculars, the huge paintings are high on the walls. On Calle dei Furlani in Castello.

Church of San Francesco della Vigna in Castello

Take a topa (little Venetian motor boat) tour: http://www.vivivenezia.org Almost two hours on the back canals.

San Giacomo dell’Orio, ceiling is wooden built with shipbuilder techniques, nice campo, northern San Polo