The story centres on the lead character, a prospector named Professor Josiah Flintabbaty Flonatin. Flonatin travels by submarine through a bottomless lake in the Rocky Mountains. While exploring the bottom of the (bottomless) lake, he discovers a strange city. Within the city, the local currency is tin, the streets are paved with gold, and the city is ruled by women. Flonatin, who is a bachelor, decides to escape the city, and does so by climbing out of a crater, which is actually an extinct volcano.