At the risk of seeming agumentative, my opinion is that you can never have too wide a lens. Especially since a wide zoom will always let you zoom in a little.
Or, put another way, a wide angle lens is to a photographer what a hammer is to a carpenter.
Florence maybe not so much, but those narrow Venetian canal "streets" just cry out for wide.
It might be a long time before you get to go again.
You lucky person, you.
Peter