Palazzo del Capitano, next to Palazzo del Popolo, is a grand building with elaborate windows built over a portico. It houses the Etruscan-Roman Museum and the Pinacoteca, art museum. The museums are closed on Mondays. The Duomo, begun in the 12th century, was built over a Roman temple. It has an outstanding central rose window. Inside are a 14th-century altarpiece, frescoes, and inlaid wood choir stalls. Behind the Duomo is a Roman house with a mosaic floor. Beyond the Duomo, near the Convento delle Lucrezia, is a great view spot. You’ll also see remains of Roman and pre-Roman walls here.