Car-choked Piazza Bocca della Verità stands on what was once ancient Rome’s cattle market, the Forum Boarium. Opposite the Chiesa di Santa Maria in Cosmedin are two tiny 2nd-century BC temples: the circular Tempio di Ercole Vincitore , the oldest marble temple in Rome, and the Tempio di Portunus , dedicated to Portunus, god of rivers and ports. Both temples are visitable by guided tour.
Just off the piazza, the 4th-century Arco di Giano is a four-fronted Roman arch where cattle traders used to shelter from the sun and rain. Beyond it is the Chiesa di San Giorgio in Velabro , a medieval church whose original 7th-century portico was destroyed by a Mafia bomb attack in 1993.
