925 Sterling Silver Pendant depicting Mouth of Truth

This sterling silver pendant depicts the pavonazzetto marble mask that was walled up in the Pronaos of Santa Maria in Cosmedin in 1632, known as the “Mouth of Truth.” While no one is exactly sure when or why the frieze was created, there are a number of theories.

Dating back to around the 1st century CE, the Mouth of Truth is a tall stone disc carved into a humanoid face with hollow holes for eyes and a gaping mouth. The original purpose of the large medallion has been theorized as everything from a ceremonial well cover, to a piece of fountain decoration, to a manhole cover.

The face itself has been said to represent a pagan god, although exactly which one is up for debate, with scholars guessing at everyone from the forest god Faunus, to the sea god Oceanus, to a local river god. While its origin remains uncertain, one unifying legend surrounding the stone carving is that if one were to stick their hand inside the disc’s mouth and tell a lie, the rocky maw would bite the offending hand off.

This belief seems to have originated during the Middle Ages, when the disc was supposedly used during trials—having the accused put their hand in the slot, and if found to be untruthful, a hidden axeman would lop off the appendage. While this story is likely apocryphal, the superstition persists to this day.

The Mouth of Truth, which now rests outside the doors of the Basilica di Santa Maria in Cosmedin, has been used as a whimsical lie detector in a number of movies and video games—most famously in the 1953 romance Roman Holiday, in which the carving served as a major plot device.