Orvieto is located on top of a large volcanic hill making Orvieto one of the best defensible places in Italy. Due to the steep incline that Orvieto is located on made it one of the last places that Julius Cesar conquered under the roman empire.
In the middle ages Orvieto was home to around thirty thousand residence.
Orvieto is home to the Orvieto Duomo. Over the years the Duomo has hosted countless popes as they traveled through out Italy.
Another advantage that Orvieto had strategically is there well system. During the sacking of rome in 1527 by the holy roman emperor Charles the fifth. Pope Clements the VII made Orvieto his hiding town. Fearing that the roman Emperor would come to Orvieto and attack or worse starve them out. Pope Clements had the well of st. Patrick begin construction. The well has the name of St. patrick because it was inspired by fact that the well should be so deep that it goes all the way down into purgatory. The Well it's self was quite the feet in civil engineering. The well was designed in a double helix fashion that allowed mules to go down to fetch the water one way and come up another with out running into the mules come down. This lead to a great effectiveness for collecting well water.