The volcano of Mysterious Island, Mount Prometheus, has become Captain Nemo's base. After traveling through its caverns and past several of Nemo's labs (which includes a diary entry of the discovery of the fossilized egg of some monstrous, unknown arthropod), guests board "Terravators" (elevators) to the facility's base station one half mile below. In this base station is a huge steam-powered bellows that pumps fresh air down from the surface, massive spring-pillars that hold the ceiling up to prevent cave-ins in case of earthquakes, and communication center which is currently giving warnings of increased seismic activity, but the scientist who mans it is currently away on a tea break.
Riders then board steam-powered mine vehicles that travel through pre-drilled tunnels into the heart of the Earth. The ride begins through a cavern of colorful glowing crystals, before entering a giant Mushroom Forest, which is inhabited by strange insect and amphibian-like life forms. Before the car can proceed further, an earthquake causes a cave-in of the tunnel ahead, forcing the car off its planned route and down a side branch filled with giant egg-like sacks that appears to have been dug by some gigantic animal. The car emerges on the shore of the Subterranean Sea, and is nearly struck by a lightning from the electrified gas clouds. The finale comes when riders are forced into the fiery heart of an active volcano, where the riders come face-to-face with the giant centipede-like lava monster that has built a nest there, before escaping back to the surface on the wave of an eruption.
Journey to the Center of the Earth was originally planned as a free-fall type ride as part of Discovery Mountain, a former Disneyland Paris concept in place of Space Mountain. Since it was never built, this project reemerged in Tokyo DisneySea with new technology.