Viterbo, Italy, styles itself as the "City of the Popes" and this Gothic-style, palace, known locally as Palazzo dei Papi, is the reason why. Most people think of Rome (or more specifically, Vatican City) as the home of the pope, but this is not written in stone.

Many people remember the abandonment of Rome during the Avignon Papacy of the 14th century. A lesser-known fact is that, because of opposition to the pope's interference in secular affairs, the commune of Rome turned against the pope in the early 13th century. For 24, years the papacy decamped to Viterbo, where they upgraded the bishops' palace to produce a residence fit for the pope. However, it seems that not all of that construction work was up to standard—in 1277, Pope John XXI died after the roof of his study collapsed and he was crushed beneath the rubble.

The most important chamber in the palace is the Sala de Conclave which was the site of the first, and longest, papal election conclave in history (it took 33 months, from November 1268 to September 1271, to select Gregory X). The people of Viterbo resorted to isolating the cardinals in the palace and reducing their food supply to force a decision.

Next to the palace is the Cathedral of Viterbo ( or Duomo) which is Viterbo's equivalent of St. Peter's Basilica. Many of the papal treasures are now housed in the adjacent Colle de Duomo Museum. The popes continued to use Viterbo as a luxurious "vacation" retreat after the papacy returned to Rome. They were fond of their luxuries and none more so than Nicholas V who, long after Viterbo was used as the main papal residence, commissioned a " bath palace" in Viterbo to make use of the thermal springs in the area.