In the novel, Professor Lidenbrock and the others descend deep beneath the earth and reach a granite wall. They blast through it, but instead of finding a passageway to the center of the earth, they encounter what seems to be a bottomless pit. They don't get to the center of the earth. Instead they are swept along by whirling, rushing water and eventually are ejected back to the surface of the earth through a volcano.
Although they don't get to the exact center of the earth, the explorers go farther beneath the earth's surface than anyone has gone before and find an uncharted world populated by dinosaurs, giant mushrooms, and primitive people, along with bodies of water nobody on the surface of the planet has ever seen before. They do have a magnificent adventure.