The Bocca della Verita is the most famous lie detector in Rome. What it is is a marble mask with a hole in the mouth, which is supposed to bite the hand of liars. Those who pass the test are allowed to enter the 8th-century Chiesa di Santa Maria in Cosmedin. The entrance was added later while the three columns that hold the nave come from the arches of an old market. Between April and September it is open from 9.00 - 18.00 and from October to March it is open from 9:00 - 17:00. The closest bus stop is "Via dei Cerchi".