Fodor's Expert Review Terme dei Papi

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.