The “Mouth of Truth” is a Roman marble medallion showing the image of a Roman bearded deity with an open mouth. The object has a diameter of about 1.75 meters and weighs 1.3 t.
The object is believed to have been able to function as an entrance to the sewer of Rome (near the Temple of Hercules) on the Forum Boarium, be part of a fountain or sarcophagus.
It is still not identified what the deity is shown on the medallion. Scientists suspect Mercury, Fauna, Jupiter or the Greek Triton and Oceanos.
In medieval times there was a legend saying that a lying person who puts his hand in the deity’s mouth would lose it. This myth has become so popular that the medallion has become a real tourist curiosity with which tourists often take a picture. It stands against the left wall of the portico of the Santa Maria in Cosmedin church in Rome.