Vicenza is a small but very pretty city, here famous architect Andrea Palladio created his masterpieces.
The main points of interest (designed by Palladio) are:
The Teatro Olimpico ("Olympic Theatre"), a Reneissance theatre with a wonderful trompe-l'oeil built by Vincenzo Scamozzi. (https://www.teatrolimpicovicenza.it/en/)
The Basilica Palladiana, the main civil building in the XVI century, with her futuristic (for those years) Loggia.
Palazzo (Palace) Chiericati that hosts the civic gallery.(https://www.museicivicivicenza.it/en/)
Villa Capra said "La Rotonda" (The Rotunda) that ispired many builings first of all The White House. (https://www.villalarotonda.it/?lang=en)
Just outside Vicenza, do not miss the Basilica of St. Mary on top of Monte Berico hill, from where you can admire Vicenza panorama.