When Hercules pushes the boulder blocking the door to Hades' throne room aside, you can enter. Talk to o Hades and ask him how can you stop Zeus. Hades will tell you he'll give you his crown because he can't leave the underworld. When you wear it, it makes you grow 2 times larger than the average Poptropican.
Garden Of The Sphinx | Grove of Temples | Hades' Realm | Hades' Throne | Hydra's Cave | Labyrinth Entrance | Labyrinth | Main Street | Mount Olympus | Pit of Hades | Poseidon's Beach | Poseidon's Realm | Poseidon's Throne | River Styx | Tree Base | Tree Top | Zeus' Throne