According to an article in the new issue of AFAR, here is what to drink where.
In Milan, it started with a Milano-Torino which is Campari and vermouth. Then it morphed into the Americano, which adds soda water. Bar Basso is recommended.
When in Florence, it's the Negroni. That's a Milano-Torino with gin. They recommend Caffe Lietta. OK that one sounds like it will knock you on your butt pretty quickly.
Venice? The Aperol Spritz of course, which has apparently edged out the Bellini in popularity. Prosecco, soda water and bitter Aperol. The Bellini being peach nectar and prosecco.
Had a Bellini and club sandwich of course at Harry's Bar many moons ago.