Claim: Poseidon used his trident to strike a rock upon the hill of the Acropolis, producing a well of seawater, which was later to be called the Erechtheis.
Evidence: Poseidon used his trident to strike a rock upon the hill of the Acropolis, producing a well of seawater, in what developed into a contest between him and Athena over possession of Attica. The well was later to be called the Erechtheis.