On your final day, head outside of Rome to explore the attractions of the Appian Way, the hill town of Tivoli, the ruins of Hadrian's Villa, and the Villa d'Este gardens.
1. Catacombe di San Callisto
Perhaps no one has ever explored all 19km (12 miles) of these catacombs, where some half a million Christians were buried from the 1st to the 4th centuries. The catacombs are webbed with 9m (30-ft.) tunnels containing these impressive tombs. After about an hour, you'll get the picture of what it's about.
Before leaving the Appian Way, we'd recommend a visit to another important catacomb:
2. Catacombe di San Domitilla
Also reached by bus no. 218, and entered at Via d. Sette Chiese 282, this is the oldest of the catacombs, containing a 3rd-century portrait of Christ and the Apostles. You enter through a sunken 4th-century church. Allow 45 minutes for a visit.
For our next attraction, we leave the city of Rome altogether, heading for the hill town of Tivoli, 32km (20 miles) east of Rome. We recommend a luncheon stopover here, preferably at a restaurant with a view over the countryside.
After lunch, head for the town's major attraction:
3. Hadrian's Villa (Villa Adriana)
The ancient ruins of the Villa of Hadrian (A.D. 135) are among the most impressive in Italy, lying some 6.5km (4 miles) from the center of Tivoli and reached by bus no. 4 or 4X from Tivoli. Allow at least 1 1/2 hours to take in the major attractions here, including the Teatro Marittimo, a circular maritime theater. Hadrian was an amateur architect, and much of the villa was designed by him.
With the time remaining, return to the center of Tivoli and for a call on the spectacular:
4. Villa d'Este
The villa, built by a cardinal in the mid-16th century, is an afterthought to the hillside gardens, among the most beautiful in Greater Rome. The gardens appear like a fairy tale of the Renaissance, using water as a medium of sculpture. There are fountains in every imaginable shape and size, the pathways lined with some 100 fountains, the stairs flanked with cascades on either side. Allow at least an hour for exploration.
Return to Rome for the evening. If you made reservations in advance and it's summer, you can attend an:
5. Opera at the Baths of Caracalla
You can head out for an opera at these ancient baths, entered along Viale della Terme di Caracalla. Take the Metro to Circo Massimo.