Still a few steps up San
Fortunato Church, San Cassiano's prison ( Carcere di San Cassiano) lies
on the Rocca, the highest part of Todi. This prison was originally a Roman
cistern . Here San Cassiano, a Christian martyr, was kept. Later it was
transformed into a church and San Fortunato's relics were kept for many
years. The entrance to the quadrangular building is through a round arched
door lying on two capitals. The two windows were added later.