you go to where you found Zeus.
To win on Mythology Island, collect all 5 of the sacred items. After they are taken by Zeus at the Tree of Immortality, get Hercules to help you reach Poseidon and Hades, then travel to fight Zeus on Mount Olympus. There is a full solution at the related question below.
You have to get Hercules to do it. He will only help you reach the throne rooms of Hades and Poseidon once you have taken the 5 sacred items back to the Tree of Immortality.
The only "secret places" are the throne rooms of Hades and Poseidon. You can only reach them after Zeus has taken the 5 sacred items. Hercules will help you move the rocks if you have the Touchscreen Mirror (pass Aphrodite's test in Poseidon's realm).
Once Zeus has taken the 5 sacred items, Hercules will agree to help you, and will move the rocks blocking the way to Hades and to Poseidon. (You will need the Touchscreen Mirror from Aphrodite in Poseidon's realm.)
To unlock the gate on Mythology Island, you need to find and collect five sacred items: The Golden Apple, Hydra's Scale, Poseidon's Trident, Aphrodite's Token, and Hades' Crown. Once you have all five items, return to the gates and use them to unlock the gate and progress in the game.
Hercules is not going to help you during the hunt for the Five Sacred Items. It is only after Zeus has taken them from you that he agrees. His contribution is to move the large rocks blocking you from the Hades and Poseidon throne rooms. He also smashes the lock on the Mount Olympus gate.
You cannot open the lock to enter Olympus. After you have found the 5 sacred items and they are taken by Zeus, Hercules will help you reach the throne rooms of Poseidon and Hades, and then smash open the lock so you can confront Zeus on Mount Olympus.
You don't. When you have recovered all 5 sacred items and taken them back to the Tree of Immortality, Zeus will grab them. Go to Hercules and he will help you reach the two throne rooms, Poseidon and Hades. (You will need the Touchscreem Mirror from Aphrodite's test in Poseidon's realm.)
Hercules is not going to help you during the hunt for the Five Sacred Items. It is only after Zeus has taken them from you that he agrees. His contribution is to move the large rocks blocking you from the Hades and Poseidon throne rooms. He also smashes the lock on the Mount Olympus gate.
He will only help you once you have taken the 5 sacred items back to the Tree of Immortality (where they are stolen by Zeus). Hercules will remove the rocks from the throne rooms of Hades and Poseidon, and open the gate to Mount Olympus. (You will need the Touchscreen Mirror from Aphrodite's test on the beach in Poseidon's realm.)
Hercules is not going to help you during the hunt for the Five Sacred Items. It is only after Zeus has taken them from you that he agrees. His contribution is to move the large rocks blocking you from the Hades and Poseidon throne rooms. He also smashes the lock on the Mount Olympus gate. When he is turned to stone by Medusa, that is where he stays when you finish the island. He may return for another adventure on Poptropica.
Hercules is not anxious to help you. It is not until you have recovered all five Sacred Items, and had them taken away by Zeus, that he agrees to help.You need the mirror from Aphrodite to go to the realms of Hades and Poseidon. Hercules will roll the stone out of the way and break the large underwater block.(* There is nothing functional at all in Herc's Hero Hut!)