We have been to Rome, Cinque Terra, Milan so do not need to repeat those. Could go first part of September
Have you looked at any of the trip reports? Do you know what you're interested in? Hard to reply without more info.
Here's the problem? We don't know anything about you; your likes, dislikes, interests, how you'd prefer to get around, or even who "we" are. A couple? Single with kids? Approx. ages?
The possibilities are endless. Help us out a little, please? :O)
From a previous post it looks like you've also been to Florence?
A good guide book will help you narrow down your options
Or start here
https://www.ricksteves.com/europe/italy
Sicily. Or Florence, Venice, Dolomites.