The Bocca della Verità, or "Mouth of Truth," is a large marble mask located in the portico of the Santa Maria in Cosmedin church in Rome, Italy. It dates back to the 1st century AD and is believed to represent the face of the river god Oceanus. The mask has a circular shape with a diameter of about 1.75 meters and features a serene expression. According to legend, the Bocca della Verità is a lie detector. If someone tells a lie while their hand is in the mouth, it is said that the mask will bite it off. This myth has made the mask a popular tourist attraction, drawing visitors eager to test their honesty.