Reservations are required to see the Giotto frescoes in Padua's Cappella degli Scrovegni—though if there's space, you can "reserve" on the spot.
On the outskirts of Vicenza, Villa della Rotonda, one of star-architect Palladio's masterpieces, is open to the public only from mid-March through mid-November, and only on Wednesday and Saturday. (Hours for visiting the grounds are less restrictive.)
Another important Palladian villa, Villa Barbaro near Maser, is open weekends and several days during the week from March to October. From November to February, it's open only on weekends.
If you plan to take in an opera at the Arena di Verona, buy tickets as early as you can, since they sell out quickly. Also, book a room for the evening in Verona, as you are likely to miss the last train back to Venice.
Making the Most of Your Time
Lined up in a row west of Venice are Padua, Vicenza, and Verona—three prosperous small cities that are each worth at least a day on a trip out of Venice. Verona has the greatest charm, and it's probably the best choice if you’re going to visit only one of these cities, even though it also draws the biggest crowds of tourists.
East of Venice, the region of Friuli–Venezia Giulia is off the main tourist circuit, but you may be drawn by its caves and castles, its battle-worn hills, and its mix of Italian and Central European culture. The port city of Trieste, famous for its elegant cafés, has quiet character that some people find dull and others find alluring.