Palazzo dei Papi is a palace in Viterbo, northern Lazio, Italy. It is one of the city's most important monuments and is located next to the Duomo di Viterbo (Viterbo Cathedral).
From 1257 to 1281 a total of eight popes resided in Viterbo almost without interruption. The commune's offer to build a palace as a curia seat for the popes contributed to this. This structure was built in sections from 1255 to 1266 and was given the name “Palace of the Popes” due to its use; today it is the Bishop's Palace.
The first and longest conclave to date took place in Viterbo. In 1268, after the death of Pope Clement IV, the conclave began, which lasted a total of 1005 days (from November 30, 1268 to September 1, 1271). The number of cardinals was initially 20 and in the end only 16, as 3 cardinals died during this time and one left the conclave. On Bonaventure's advice, the cardinals were eventually confined to bread and water until a new pope was elected. On September 1, 1271, a non-cardinal was elected as the new pope. The chosen one, Tebaldo Visconti, an Italian from Piacenza, not even a priest, was at that time on a pilgrimage in the Holy Land (Acre). Visconti, then archdeacon of Liège, arrived in Viterbo on February 10, 1272, accepted the election, was ordained a priest and bishop on March 19, 1272 and was crowned as Pope Gregory X in Rome on March 27, 1272.
In Viterbo. resident popes:
Alexander IV, Pope from 1254 to 1261 (stable residence in Viterbo from 1257);
Urban IV, Pope from 1261 to 1264 (divided his residence between Orvieto and Viterbo);
Clement IV, Pope from 1265 to 1268 (almost always lived in Viterbo);
Gregory X, Pope from 1271 to 1276 (Gregory
Innocent V, Pope from January 21 to June 22, 1276 (stayed in Viterbo for two weeks, shortly after his election, and met Charles of Anjou there);
Hadrian V, Pope from July 11, 1276 to August 18, 1276 (spent almost all of his short pontificate in the monastery next to the church of San Francesco alla Rocca);
John XXI, Pope from September 15, 1276 to May 20, 1277 (almost always lived in Viterbo);
Nicholas III, pope from 1277 to 1280 (divided his residence between Viterbo, Rome and Soriano nel Cimino);
Martin IV, elected on February 22, 1281 (left Viterbo immediately after his election).