Poseidon used his trident, which was forged by the cyclopes according to Pseudo-Apollodorus's Bibliotheke, to strike a rock upon the hill of the Acropolis, producing a well of seawater, which was later to be called the Erechtheis.
The trident of Poseidon and his Roman equivalent, Neptune, has been their traditional divine attribute featured in many ancient depictions. In Greek myth, Poseidon's trident was forged by the cyclopes according to Pseudo-Apollodorus's Bibliotheke. 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. 
