There are many day trips to nearby towns and cities that you can take from Rome. Florence, Frascati, Tivoli, and Ostia Antica are among some of my favorites. Taking the train from Roma Termini Station to Tivoli, located about 30 km to the northeast from downtown Rome, takes about 45 minutes. As the train pulls out of the station and moves into the country you see parts of the city you normally wouldn’t experience and finally as you climb the gently curving hills toward Tivoli you can look forward to beautiful vistas including some waterfalls.
Among Tivoli’s many treasures are Villa d’Este and Villa Adriana (Hadrian’s Villa). Both exceptional in what they have to offer. If you have to choose, Villa d’Este, would be my choice for the exquisite fountains, vistas, and greenery. (NOTE: Villa d’Este and Villa Adriana are closed on Mondays)
Upon arriving at the Tivoli Train station walk downhill on Viale Giuseppe Mazzini. When you arrive at the traffic circle, round the circle to your right, and stop at Il Ciocco for an espresso. From the back of the bar you can look down upon Villa Gregoriana. From here you can follow the signs to Villa d’Este and enjoy your walk up into this ancient town.