Cerberus

 
Monster of the Greek mythology, son of Typhoon and Echidna. He had a snake’s tail and three dog’s heads. Cerberus used to guard the gates of Hades, the Underworld. Only once was he made to leave his post by Hercules and this was the hero’s most difficult labour.
 
The sculpture of these three hounds can be found in the town of Leutenberg in Germany.