The Mouth of Truth / Bocca della Verità is an ancient Roman marble disc with a relief carving of a man's face.
According to legend the face's mouth closes if a liar sticks his hand in it.
The massive marble mask weighs about 1300 kg and probably depicts the face of the sea god Oceanus. The eyes, nostrils and mouth are open.
Audrey Hepburn and Gregory Peck in Vacanze Romane, 1953