Otto Lidenbrock is a character in 80 Days, a scientist and explorer looking to investigate the world beneath the Earth's crust.
Otto is an inquisitive professor who believes there is a world beneath the earth's crust, and searches for ways to better explore this unknown place.
After striking up a conversation with Passepartout in the underground city of Kristiania, Otto mentions that he is looking around the globe for entry points into the Earth's core. Passepartout recommends Iceland, famous for its volcanic instability and geysers, and Otto thanks him for the suggestion. Sure enough, upon arriving in Reykjavik, Passepartout runs into Otto again - Otto was waiting for a cargo delivery aboard the same airship on which Passepartout and Fogg were travelling.
Otto reveals that he has indeed discovered a world beneath the surface of the Earth, with exit points in Kristiania, Reykjavik and, most crucially, Snowden - allowing Passepartout and Fogg to travel there at great speed aboard an underground boat. If they do not decide to go with Otto, they may be given a Spherical Diamond instead.
Otto is steadfast and hard to distract from his aims, being unfaltered from his notions despite any skepticism Passepartout may express. He is happy to talk at length about his study and takes any interest seriously almost to a comedic extent, as shown when he acts on the halfhearted suggestion to 'try Iceland'.