Palazzo dei Papi (Viterbo)

The Palazzo dei Papi in Viterbo was built from 1255 to 1266 as a residence for the popes, who often lived in the city in the 13th century. It was the site of the papal election of 1268–1271, the longest in history, during which the citizens locked the cardinals in and removed the roof, which led to the rules of the conclave.