The cryptogram of St. Nicholas, still not understood, is one of the mysteries present in the Nicolaian Citadel. In the right transept of the Basilica of St. Nicholas there is a silver altar that originally covered the tomb of the saint. The altar dates back to 1319, a gift from the Tsar of Serbia Uroš II Milutin, and for about three hundred years it has housed a unique enigma. On one of the different levels of the altar there is a lamina with a floral motif, framed by 642 continuous characters whose meaning is unknown to date.
Many believe that it is a cryptogram, that is, an encrypted message. Many hypotheses have been made about the meaning of the message: a message from the Knights Templar, a love proposal, a request for help in arms, even a reference to the Holy Grail.
To date, no one has been able to provide a convincing solution to the enigma, and therefore the most likely hypothesis remains that of an inscription without any meaning, perhaps deliberately unsolvable and conceived by the author as a “puzzle” to be provided to posterity.