Italy · 18th Century
Siena
On August 14, 1730, on the vigil of the Feast of the Assumption, thieves broke into the Church of St. Francis in Siena—the city of St. Catherine, the great Doctor of the Church who, according to tradition, subsisted on the Eucharist in her final years—and stole a golden ciborium containing 351 consecrated Hosts. Three days later, on August 17, the Hosts were discovered intact in the alms box of the Sanctuary of Santa Maria in Provenzano, covered in dust but otherwise unharmed.
About this miracle
The Hosts were returned to the Church of St. Francis and placed in the tabernacle. What happened next has defied scientific explanation for 295 years: the Hosts have remained whole, shiny, and fresh, maintaining the characteristic scent of unleavened bread. They are not dried out, not moldy, not decayed—still quite consumable. According to Catholic teaching, since they maintain the appearances of bread, these Hosts consecrated in 1730 remain the Body of Christ.
In 1914, Pope Pius X authorized a comprehensive scientific investigation led by Professor Siro Grimaldi of the University of Siena. The commission determined the Hosts were made of ordinary wheat flour with no special preparation. Their report concluded: 'The sacred Hosts of Siena are the classic example of the perfect conservation of particles from unleavened bread consecrated in the year 1730, and constitute a unique phenomenon, full of interest which reverses the natural laws of conservation of organic matter.'
Crucially, during the 1789 investigation under Archbishop Tiberio Borghesi, a control experiment was begun: unconsecrated hosts were sealed and kept under comparable conditions. When examined about ten years later they were found decayed and disfigured — showing that ordinary hosts deteriorate within a decade under comparable conditions.
Further scientific examinations in 1922 and 2014 (the latter using digital microscopy and ATP testing) confirmed no decay; the Hosts were also recounted after a 1950 ciborium transfer and a 1951 theft of the ciborium (in which the Hosts themselves were left behind). Of the original 351 Hosts, 223 remain perfectly preserved today—an impossibility for organic matter nearly 300 years old.
Pope John Paul II visited Siena on September 14, 1980, for the miracle's 250th anniversary and said of the preserved Hosts: 'It is the Presence!' (rendered in some English accounts as 'It is the Real Presence!'). The Hosts are displayed publicly on the 17th of each month (commemorating their discovery) and carried in procession through Siena's streets on the Solemnity of Corpus Christi, continuing a 295-year witness to the mystery of the Eucharist.