In 1207, Pope Innocent III held a council in the cathedral, but the city was later excommunicated as the favourite seat of the heretical Patarines and even defeated by the Romans.

Frederick II drew Viterbo to the Ghibelline side in 1240, but when the citizens expelled his turbulent German troops in 1243 he returned and besieged the city, but in vain.

Other popes elected in Viterbo were Gregory X (1271) and John XXI (1276) (who died in the papal palace when the ceiling of the recently built library collapsed on him while he slept), Nicholas III and the French Martin IV.

The Viterbese, who did not agree with the election of a foreigner directed by the King of Naples, Charles I of Anjou, invaded the cathedral where the conclave was held, arresting two of the cardinals.

In the fourteenth century, Giovanni di Vico had created a seignory extending to Civitavecchia, Tarquinia, Bolsena, Orvieto, Todi, Narni and Amelia.

[11] In the valley of the Arcione River just to the west of Viterbo are a number of springs celebrated for the healing qualities of their waters, and in use since Etruscan and Roman days.

[12] In fact, the imposing ruins of a great Roman bath are still to be seen and were drawn in plan and perspective by Renaissance artists including Giuliano da Sangallo, Michelangelo, and Vasari.

[13] One of the most famous were the thermal springs known as the "Bullicame", or bubbling place, whose reputation had even reached the ears of the exiled poet Dante Alighieri.

Canto 14 (lines 79–81) of Dante's Inferno describes how: In silence we had reached a place where flowed a slender watercourse out of the wood—a stream whose redness makes me shudder still.

[15] Actually, the origins of this bathing establishment date to the Middle Ages when it was known as the Bagno della Crociata (named either after a Crusader who supposedly discovered the spring or from a corruption of the Italian word for crutch).

[16] A more precise description of Pope Nicholas' palace was described by the Viterbese chronicler Niccola della Tuccia in the 1470s, who stated the new Bagno del Papa as a battlemented building, resembling a fortress, about 30 x 20 m in size with high towers at the corners of its southern façade.

To the contrary, Vatican payment records from 1454, preserved in the state archives in Rome, identify a stonemason from Lombardy, named Stefano di Beltrame, as the builder who "had done or was doing in the house ordered by the pope at the bagni della Grotta and Crociata of Viterbo.

[19] Travelers' descriptions, etched views, and local guidebooks chronicle the fate of the Renaissance Bagno del Papa over the years and through several rebuildings resulting in a general assumption that most of the original 15th-century structure had vanished.

[20] Despite all the travails, much of the original Bagno del Papa built by Popes Nicholas V and Pius II survives, including the corner towers and the vaulted chambers where Renaissance patrons once bathed.

At the top of the tower, the statue of the patron saint is enthusiastically acclaimed by the people in the streets of the town centre, where lights are turned off for the occasion.

One hundred Viterbesi men (known as the Facchini) carry the Macchina from Porta Romana through each of the major streets of Viterbo to seven churches to be blessed, concluding with a strenuous ascension up to the Piazza di Santa Rosa, its final resting place.

On 26 November 2007, Italian transport minister Alessandro Bianchi announced that Viterbo had been chosen as the site of the next airport in Lazio to serve Rome.