Palazzo dei Papi: site of history's first and longest papal conclave

The Palazzo dei Papi, also known as the Palace of the Popes, is a significant monumental palace located in Viterbo, Italy. Built in the 13th century, it was enlarged to accommodate the papal residence, as the Papal Curia was moved to Viterbo by Pope Alexander IV in 1257 due to the hostility of the Roman commune and constant urban violence.

The construction of the palace was commissioned by the Capitano del popolo, Raniero Gatti, and it provided a great audience hall communicating with a loggia raised on a barrel vault above the city street. It was completed probably around 1266. The palace remains one of the most important monuments in the city, situated alongside the Duomo di Viterbo (Viterbo Cathedral).

The palace was the residence of the papacy for twenty-four years, from 1257 to 1281. It housed various popes including Urban IV, John XXI, and Nicholas III. It is home to the Sala del Conclave, the famous hall where the first and longest conclave in history took place between 1268 and 1271, resulting in the election of Gregory X.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons