Oedipus and the Sphinx, oil on canvas by Gustave Moreau, 1864. Oedipus was a mythical Greek king of Thebes. A tragic hero in Greek mythology, Oedipus fulfilled a prophecy that said he would kill his father, and thereby bring disaster on his city and family. On his journey to Thebes, Oedipus encountered a Sphinx, who would stop all travelers to Thebes and ask them a riddle. If the travelers were unable to answer her correctly, they would be killed and eaten; if they were successful, they would be free to continue on their journey. The riddle was: "What walks on four feet in the morning, two in the afternoon and three at night?". Oedipus answered: "Man: as an infant, he crawls on all fours; as an adult, he walks on two legs and; in old age, he uses a 'walking' stick". Oedipus was the first to answer the riddle correctly and, having heard Oedipus' answer, the Sphinx was astounded and inexplicably killed herself by throwing herself into the sea, freeing Thebes from her harsh rule.