Archaeologists digging in Turkey have found the guardians of the "Gate to Hell" -- two unique marble statues which once warned of a deadly cave in the ancient Phrygian city of Hierapolis, near Pamukkale. Known as Pluto's Gate -- Ploutonion in Greek, Plutonium in Latin -- the cave was celebrated as the portal to the underworld in Greco-Roman mythology and tradition. It was discovered in March by a team led by Francesco D'Andria, professor of classic archaeology at the University of Salento.