Once you have recovered the 5 sacred items and Zeus takes them, you can get Hercules to help you at last. He will kick away the large rock to reach Poseidon, and also move the boulder to let you reach Hades. Once you have the Trident and the Hades Crown, Hercules will also smash the padlock on the Olympus gate.
Poseidon is found on Mythology Island, which is a Poptropica island.
From Poseidon's statue in the museum.
the pink starfish
In Poseidon's realm, you click on her.
It is in the museum, on the face of Poseidon's statue.
The only doors on Mythology Island are at the temples of Hades and Poseidon, and on the Minotaur's lair.
If you are talking about Mythology Island, there is no such thing there. Mythology Island only has three 'kingdoms': Hades, Poseidon, and Zeus.
Offer the starfish from the Poseidon statue in the Museum.
The offering for Poseidon is a starfish. There is one on the face of his statue in the Museum of Olympus.
zombie poptropica
all you need is Hercules's help
You need a starfish. There is one on Poseidon's statue in the museum on main street.