There are so many it is hard to pick just one.
Tuscany is amazing.
Cinque Terre is beautiful.
Venice is like nothing you've ever seen.
The Dolomites are unbelievable.
The Amalfi Coast is stunning.
Rome is truly eternal.
Florence is an art lovers paradise.
Capri is heaven on earth.
They're all worth visiting and "must see" places in my opinion.