Don Lazzaro of Verona, a Camaldolese monk at the abbey church of Santa Maria Assunta in Bagno di Romagna, was celebrating Mass in 1412 when, distracted by spiritual dryness and doubts about the Real Presence, he was about to put down the chalice after the consecration. At that moment he saw the wine bubble up and seethe in the chalice, then transform visibly into red blood that rose to the rim and stained the corporal beneath the chalice.
Don Lazzaro fell to his knees. The bloodstained corporal was preserved; the chalice itself, in pewter, became an object of veneration. The relic is still kept in the basilica, which holds an annual celebration on the third Sunday of May. The miracle was confirmed by the Camaldolese authorities and recognised by the local bishop.