4 Best Sights in Side Trips from Rome, Italy

Viterbo has been a spa town for centuries, and this excellent complex not far removed continues the tradition, providing health and beauty treatments with an Etruscan twist: try a facial with local volcanic mud or a steam bath in an ancient cave. The main draw, however, is the 21,000-square-foot outdoor limestone pool, into which Viterbo's famous 59°C (138°F) mineral water pours—and gives a jolt with its sulfurous odor.

You can rent floats and deck chairs, but bring you'll need your own bathrobe and towel unless you're staying at the hotel. Tickets tend to sell out but can be booked online up to five days ahead of your visit. Shuttle buses operate between Rome's Piazza del Popolo and the terme on weekends and holidays. Round-trip tickets cost €12.

Viterbo's Romanesque cathedral was built over the ruins of the ancient Roman Temple of Hercules. During World War II, the roof and the vault of the central nave were destroyed, and you can still see the mark the shrapnel left on the columns closest to the pulpit. Subsequently, the church was rebuilt to reflect its medieval design, and it still has many original details, including a beautiful Cosmati floor that dates from the 13th century.

Three popes are buried here, including Pope Alexander IV (1254–61), whose body was hidden so well by the canons, out of fear that it would be desecrated, that it has never been found. The adjoining Museo del Colle del Duomo has a collection of 18th-century reliquaries, Etruscan sarcophagi, and a painting of the Crucifixion that has been attributed to Michelangelo. The ticket to the museum also grants you entrance to the Palazzo Papale, located on the same square.

This Gothic palace was built in the 13th century as a residence for popes looking to get away from the city. At the time, Rome was notoriously ridden with malaria and the plague, not to mention rampaging factions of rival barons. In 1271 the palace was the scene of a novel type of rebellion. A conclave held that year to elect a new pope dragged on for months. The people of Viterbo were exasperated by the delay, especially as custom decreed that they had to provide for the cardinals' board and lodging for the duration of the conclave. To speed up the deliberations, the townspeople tore the roof off the great hall where the cardinals were meeting, and put them on bread and water. A new pope—Gregory X—was elected in short order.

Today, you can visit the great hall, step out on the pretty loggia, and admire the original frescoes in the small adjoining room. An audio guided tour is free with the purchase of a ticket and lasts 45 minutes, starting from Museo del Colle del Duomo.

One of the best-preserved medieval districts in Italy, San Pellegrino has charming vistas of arches, vaults, towers, exterior staircases, worn wooden doors on great iron hinges, and tiny hanging gardens. You pass many antiques shops and craft workshops, as well as numerous restaurants, as you explore the little squares and byways. The Fontana Grande in the piazza of the same name is the largest and most extravagant of Viterbo's Gothic fountains.