In the 13th century, most popes preferred to live in the medieval village of Viterbo, located in central Italy.
At the time, the town was far removed from the pressures and the plague that made Rome inhospitable.
So in 1268, cardinals met in a village palace to chose a successor to Pope Clement IV.
"It took them a while to make a decision," Monsignor Salvatore del Cicuo told an ABC News translator in Italian. "Two years and eight months. The longest conclave in history!"
Monsignor Charles Burns, a retired archivist at the Secret Vatican Archives, added, "The people of Viterbo were so annoyed by this, they said, "OK, we are going to close the cardinals in.' "
The term "conclave" literally means "with a key."
"The idea was to make it uncomfortable to persuade cardinals to get on with the job," said Burns.
Even then, Ciuco said, the cardinals still could not decide. So villagers tried to starve them out. Eventually, they even tore the roof off the building.
"Someone joked it would let the Holy Spirit in," Ciuco said.
The conclave eventually chose Gregory X as its new pope. But he was not a cardinal nor a priest; he was a crusader off fighting in the Holy Lands. It took him eight months to return from the battlefield.
One of his first acts as pope was to establish strict rules to ensure faster conclaves in the future.
Pope John Paul II changed the rules in 1996. Cardinals will be allowed to leave the Sistine Chapel during the current conclave, and they will eat and sleep in relative comfort.
Some worry that could lengthen the conclave.
"One never knows," said Burns. "I don't think that will happen. But one never knows."
ABC News' David Wright filed this report for "World News Tonight."