Shraddha Ranganathan

Miracle (buster!) on Kalverstraat

Why is Amsterdam still celebrating a 674-year-old miracle? And how much of a miracle is it really?


In 1967 trok de Stille Omgang 14.000 deelnemers - © Cor Out/ANP


The 1300s were a good time for miracles. Religion was all the rage, and science was considered witchcraft, so anything that you couldn’t immediately explain, was deemed God’s work. What a magical time! A weeping statue here, a bleeding picture there…every city, every church had a miracle to show off. Not to be left behind, Amsterdam also has a favorite miracle – of course, with a touch of ridiculousness, and a yearly celebration. 


Here is what we know:

  • The year is 1345, and in mid-march at midnight, a man is dying.
  • He calls for a priest. Obliging, the priest performs the necessary rites, and gives our man a sacramental wafer.
  • Later that night, he gets violently sick and empties the contents of his stomach (including the holy wafer) for a poor housekeeper to clean up.
  • The housekeeper, a God-fearing Christian, knows that the only way to dispose of something blessed, is to burn it, so she dutifully puts the vomit in the fireplace. Job done, she goes home. When she returns the next morning, she finds wafer in the fireplace, unburnt.
  • She reaches into the fireplace and somehow grabs the wafer without burning herself.
  • The priest is called back, and takes on the responsibility of taking this miraculous wafer to the St. Nicholas church (now Oude Kerk).
  • The stubborn wafer refuses to be quietly put away, and reappears in Kalverstraat in the morning. The priest tries again to secretly take it to the church, but to no avail.
  • The church hears the divine message that the miracle will not be hidden, and transports the wafer from Kalverstraat to Oude Kerk with a grand procession that’s celebrated every year – the Stille Omgang.

    Old etching depicting "the Miracle of Amsterdam" -


Knowing what we know today, we can piece together the logic behind this mystery, with the help of one miraculous microorganism.

Back in 1345, the priest, called away on emergency, quickly throws together his holy bag – his rosary, his bible, holy oil, sacramental bread, everything he can think of. He doesn’t pause to check any of the components, and there begins our miracle. Unbeknownst to him, mold of some kind (probably the common Aspergillus) has grown within the wafer and on the surface. Fungi are tenacious things – they have an efficient method of putting down roots (or, mycelia) that propagate quickly through the host.


Our unlikely hero, Aspergillus spp. -

Now, as the priest is finishing the last rites, the dying man gratefully accepts the moldy host, and everyone is happy (including the fungus, which now has a warm, wet place to grow). Sick as he is, maybe he simply wasn’t able to digest the wafer. Maybe his immune system was fighting a chaotic war, or maybe the fungus had become functional enough to release toxins that made him sick to the stomach. All reasonable paths to the same result – our man has vomited the communion bread up, still whole.  

In to the fire it goes, as all blessed things must. Noticing that it has remained unburnt, the housekeeper immediately sees it for the miracle it is. But, we know something she didn’t – fungal mycelia are rich in lignin, silica and phosphorous. These are all components that char easily. And if the altar bread is charring on the surface, then it isn’t able to catch fire. Besides, when the housekeeper reached into the fire and grabbed the wafer, she didn’t burn herself. That clues us in to how strong that fire really was. With the weak fire, the sick man, and the many magical properties of fungi, we can quickly break down the illusion of the miracle.

The truth is that some fungus or the other is easily found, no matter where you are. In the wet, not-very-sanitary Amsterdam of 1345, maybe even more so. Besides, fungi have been responsible for many a religious experience – from ergot-related witch hunting[3] in medieval Europe, to modern rabbis taking magic mushrooms for science. To my mind, it's not a stretch to imagine that this the humble fungus could be the unsung hero behind this miracle.


Perhaps the miracle in this situation is simply delivery of the moldy wafer to a sick man, or perhaps it’s the very existence of mycelia. And although this plucky microorganism can’t explain the mysterious return of the wafer to Kalverstraat, I think we can forgive it, because every good miracle needs a mystery. 

If nothing else, it has permitted the miracle to burn on.