Rome is excelent if you like history and monuments. Pisa and Florence (Firenze) are ok two for monuments. Never been in Venice but I guess it is a must. Milan is the town I saw more street hookers per square feet
About Spain: If you plan to visit cities I recommend Madrid, Sevilla and Barcelona. If you want to go to the beach I recommend Benidorm or the Balear Islands (Mallorca, Menorca and Ibiza). Cool day at the beach, wild night.
Enjoy your trip