Cascia is known by all as the city of St Rita. It is known as well as the place where a relic of an extraordinary Eucharistic miracle which happened in Siena in 1330 is preserved.

A priest was called to administer the Holy Sacraments to a dying man in a suburb of Siena. He took a consecrated host to give him Communion. He placed it rather irreverently between the pages of his breviary, which he tucked under his arm and went to the home of the sick man.

After hearing the man's Confession, the priest opened his breviary to take the host. He was astonished to see that it had turned red with blood, which stained both pages of the breviary where it had been placed.

The priest was confused. He went to the Augustinian monastery in Siena to tell the whole story to Blessed Simon Fidati of Cascia, a well known preacher. After hearing the priest's story and seeing the miraculous sign with his own eyes, Blessed Fidati pardoned him and asked him for permission to keep the two pages of the breviary stained with the miraculous blood. Later, he took one of them to Perugia and the other to St Augustine's in Cascia. From St Augustine's the Eucharistic relic was taken to the Basilica of St Rita.

This Eucharistic relic has always been venerated by the faithful. Various Popes promoted its cult with special indulgences, including that of Portiuncula by Pope Boniface IX in 1401.

This miraculous event is commemorated every year on the feast of Corpus Christi, when the relic is carried solemly in procession.

In 1930 on the sixth centenary of the event, a Eucharistic congress of the diocese of Norica was held in Cascia. On that occasion, a precious artistic monstrance for the relic was made.