Greek Mythology/Stories/The Sphinx
The Sphinx was a creature that had the body of a winged lion, and the face of a woman. She terrorized the city of Thebes like this: she would ask anybody traveling on the road to Thebes a riddle. If they answered it, she would let them go. However, if they didn't say the right answer, she would kill them. This continued for a long time, until one day, a stranger by the name of Oedipus encountered the Sphinx on the way to Thebes. The sphinx asked him this riddle: What creature goes on four feet in the morning, two at noonday, and three in the evening?
Oedipus correctly answered man, and the sphinx killed herself.
(The answer to the riddle is man, since a man crawls on four feet when he is very young [morning], walks on two feet in the middle of his life [noonday], and walks with the help of a cane [the 'third leg'] near the end of his life [evening])