What has 6 eyes, 3 mouths, but only 1 name?

Source: INFERNO MOVIE | TAKE THE JOURNEY THROUGH HELL

To begin your journey into hell, can you help Langdon determine the city of his whereabouts?

Florence

Who doomed Dante to the Second Circle?

Beatrice

What has 6 eyes, 3 mouths, but only 1 name?

Cerberus