The historic centre, set on the highest part of a tufaceous cliff, dominates the Tiber river valley (in the eastern part of the Tuscia area of Viterbo).

In the intricate labyrinth of alleys and squares, between aristocratic buildings and modest houses, we can discover the delightful details of ashlar doors, papal and noble coats of arms, blind arches, flowered balconies, stone garlands, the closed alley of Suburra and Porta di San Cesareo, the only extant medieval gate.

The cathedral of Santa Maria Assunta, dating to the turn of the eighteenth century and featuring an early twentieth-century facade, is notable. Inside, in addition to an eighteenth-century altarpiece depicting Our Lady of the Assumption and Martyrs by Giuseppe Bottani, we can also admire a copy of the Praying Madonna by Taddeo di Bartolo. Also interesting is the church of Sant'Agostino (twelfth-thirteenth century), which has a fifteenth-century wooden cross and Our Lady of the Rosary by Giorgio da Orte (sixteenth century). The church and hermitage of Santissima Trinità, set amidst dense vegetation in the immediate vicinity, is highly evocative.

There are numerous palaces, dating to various periods, grouped around the cathedral: Palazzo Alberti (sixteenth century) with an elegant spiral staircase, Palazzo Roberteschi (fifteenth century), now the headquarters of the Ottava Medioevale Association with a library on medieval and Renaissance studies, Palazzetto dei Giuda with the portico and columns, Palazzo Nuzzi (seventeenth century), which is today the city hall.

In the former Romanesque church of San Silvestro, a noteworthy Museum of Sacred Art has been set up. The following works are exhibited there: a polyptych on the Life of St. Giles dating to the fifteenth century, done by the school of Lorenzo da Viterbo; the Madonna by Taddeo di Bartolo dated 1420; St. Francis and stories from his life, a tavola dated 1282; Madonna with Child, a tavola with arabesques by Antonio del Massaro and dating to the beginning of the sixteenth century; the Saviour Benedictory dating to the fifteenth-sixteenth century; the Annunciation by Domenico Velandi da Viterbo (1501); Madonna with Child and one of the faithful, dated 1484; the Risen Christ with John the Baptist and St. Lawrence dating to the sixteenth century; Madonna with Child and the Saints by the Flemish school of Francesco da Castello (sixteenth century); Our Lady of the Faithfuls, by Giovan Francesco d'Avanzarano (fifteenth-sixteenth century); the Saviour Benedictory by Domenico Velandi (1491); a mosaic by the Byzantine school, dating to the eighth century (portraying the Virgin Mary); sacred paraments and various reliquaries