Orvieto
This little city perched on a rock in southern Umbria offers all the best of small-town Italy, perfectly preserved for modern travelers. Amble through Etruscan ruins on the outskirts of town. Wander the cobblestone center, which is closed to cars. Indulge in locally made wine and cheeses and crafts. Tour an 11th-century city hall and 13th-century gothic basilica. Also, the city is a charter member of Italy's "Slow Food" movement, and is indeed a great place to slow down. And eat. Try lunch at the Trattoria della Grotta on Via Signorelli Luca.
Most (but not all) of the trains bound from Rome to Florence and Milan stop at Orvieto. The train station is below the historic part of the town, but a regular shuttle bus will take you up the steep road to the scenic center. You can also drive up Italy's main arterial highway, the A1, exiting at Orvieto.