The Orsini Castle, built by Orso Orsini in the 13th century. It was the summer residence of Pope Nicholas III, uncle of Orso. It was a high security castle until the 1990s and is now managed by the University of Viterbo.
The Palazzo Chigi-Albani (16th century), designed by Ottaviano Schiratti. The interior houses the Papacqua Fountain.
The small Romanesque church of San Giorgio (11th century).
Cathedral (Duomo), of San Nicola di Bari from 1794.
Church of Sant'Eutizio.
Fontana Vecchia ("Old Fountain"), built in the 15th century.
Porta Romana ("Roman Gate"), a copy of the Porta Pia in Rome.