The Forum, St. Peter's Basilica, the Spanish Steps, Trevi Fountain, the Pantheon, and the Colosseum and that's just the world-renowned sites of Rome. Picnic at Villa Borghese Gardens or walk around the Trastevere neighborhood for a bit more relaxed Rome.
Florence is fantastic for art, architecture, wine, food and shopping. A trip to Florence inspires, if you're a fan of the Renaissance or a shopaholic. Be sure to take a trip out into the Tuscan countryside, visit a few of the smaller villages and get a taste of life in Chianti.
St. Mark's Square, St. Mark's Basilica, Rialto Bridge and the Gondolas rides are the major sites in Venice. Doge's Palace impresses with the art work of Tintoretto, Titian, Bellini, and Veronese, then walk over the Bridge of Sighs to visit the prison where Casanova was held for over a year until his escape.