It is one of the most important monuments in the city, situated alongside the Duomo di Viterbo. The Papal seat has been moved in 1257 by Alexander IV due to the hostility of the Roman commune: the former Bishops Palace was thus enlarged to provide the Popes with an adequate residence. The construction, commissioned by the Capitano del popolo ("People's Capitain") Raniero Gatti, was completed probably around 1266.
The massive façade, facing the central San Lorenzo Square, is preceded by a staircase completed in 1267. On the right side is a wide loggia with seven arcades, supported by slender doubled columns and decorated with crests and reliefs. The top of the walls is decorated with square merlons. On the loggia is also a 15th century fountain, made with material of various ages, sporting the coat of arms of the Gatti family.
After Alexander IV, the palace was the seat of Urban IV, Gregory X, John XXI (who died in the building in 1277 when his study collapsed), Nicholas III and Martin IV, who moved to Orvieto in 1281. They were all elected in the most famous hall of the palace, the Sala del Conclave.

One of the most outstanding monuments in town, with a peculiar Longobard bell-tower. In the interior, a large staircase leads to the altar, dominated by three high barrel-vaults supported by two majestic columns.

According to a legend, the sarcophagus on the facade hides the body of the Bella Galiana, a beautiful woman killed by a rich lord who had fallen in love with her, but didn't manage to win her heart. In the interior, canvases, paintings and sculptures dating from XII to the XVII centuries.

One of the most outstanding monuments in town, with a peculiar Longobard bell-tower. In the interior, a large staircase leads to the altar, dominated by three high barrel-vaults supported by two majestic columns.

The cathedral was, according to legend, built on the site of an Etruscan temple to Hercules and although this can not be verified, Etruscan and Roman foundations can be seen on several of the buildings which make up the Plaza di San Lorenzo where the duomo is situated. An early medieval parish church to Saint Lawrence had formerly occupied the area before construction began on the cathedral in the late twelfth century. Even as the duomo was constructed, the town was already spreading northwards down the hill, leaving the plaza somewhat isolated on the highest edges of town, thus restricting it’s attraction to the townsfolk, a disadvantage which the local bishops for years attempted to reverse by granting the cathedral special religious privileges. The cathedral was at the height of its significance during the middle and end of the thirteenth century, when it and the attached Palazzo dei Papi di Viterbo was the home of the papal throne following its flight from Rome and prior to its resettlement in Avignon. Two popes are known to have been buried in the duomo, and others may have been during the period between 1261 and 1277. The first of these popes was Pope Alexander IV, whose tomb was bizarrely demolished during sixteenth century renovations, and the location of his remains are now unknown save that he lies somewhere inside the church. Pope John XXI is more clearly marked despite several relocations, with a handsome tombstone originally laid over him following his death in 1277 when his study in the papal palace attached to the cathedral suddenly plummeted into the hall below due to structural weaknesses. The duomo as built in the twelfth century is east-facing and sits high on the hill with the attached Papal palace overlooking the town spread below. Its façade oddly contrasts with surrounding buildings as it is not built from local stone, instead constructed with imported materials during Gambarra’s reconstruction. It is sparsely decorated, but at its centre is a rose window, although without any from of stained-glass decoration. There are two similar but smaller windows positioned further down over two smaller entrances aside the main entrance, again undecorated. The only indication of the original decoration of the cathedral can be seen on the neighboring campanile, which is clad in alternating bands of local white travertine and blue-green basalt stone in a manner similar to the entire Duomo di Orvieto. During the middle of the sixteenth century, the cathedral came under the power of a Cardinal Gambarra, scion of a wealthy Italian family who paid for extensive reconstruction of the medieval building, including the demolition of the façade, roof and central apse (including a Papal tomb). He also knocked holes in the walls to create extra chapels and replaced much of the internal art, wood and stone decorations as well as the stained glass windows. Prominent amongst his new decorations were depictions of seafood, especially lobsters and prawns, giving the land-bound cathedral a strangely nautical look. (His name Gambarra translates as prawn from the Italian, and seafood featured heavily on his coat of arms). In 1861, a further bishop also replaced the ceiling, lowering it to disguise the intricate truss and beam work of Gambarra’s creation. Much of this heavy-handed work has since been removed or replaced with what remains of original furnishings, especially following the Second World War, during which the cathedral and the city in general were quite heavily damaged by Allied bombing raids and the shelling of both sides. The cathedral lacks many of the famous artworks which make its Italian contemporaries so famous, largely due to its relatively recent renovation. The main works which line the apse are post-renovation pieces by the local artist Giovanni Francesco Romanelli during the eighteenth century as well as several more by his contemporaries. Only two notable early artworks survive, a painting of Redentore benedicte (Christ giving a blessing) from 1472 thought to be the work of Gerolamo da Cremona and a Madonna with child, which appears to be an earlier version of the famous painting in the Basilica di Santa Maria Maggiore in Rome. It has been moved here from the Viterbese parish church it was painted in during the late twelfth century, although the artist remains unknown. The cathedral also posses and impressive baptismal font constructed initially by Francesco da Ancona in 1470 before later additions.

The Museo Civico houses many archeological specimens from the pre-historical to Roman times, plus a Pinacoteca (gallery) with paintings of Sebastiano del Piombo, Antoniazzo Romano, Salvator Rosa, Antiveduto Grammatica and others.
Piazza Crispi, 2 - Tel. 0761.348275