I visit Venice for about five times because of the Art Bienale. We were there for a week and didn't go to the San Marco in the first place because we've been there before and it's sooooo crowded.
But you can't come to Venice without being on the San Marco, so we did. And yes it was crowded but in the end it's just a beautiful square.
On the bridge of sighs, which is a connection between the old prisons and the Doge's Palace, was a big advertisement from Sisley.
I looooved it, it looked so amazing. The blue sky, the clouds and the models from Sisley against the old white buildings.
Just blew me away.