What is the story Poseidon and Athena?

well Poseidon is Athena's uncle and the story is that they both both wanted be the gods of Athens (even though Athena found it) so they made the people chose and they Athena won over Poseidon because she made the olive tree and Poseidon made a water horse or a fountain ( I'm not so sure but if you want the full story you should read Percy Jackson) (in order or you won't understand!) -Claudia