“Land of Sannikov”. Since ancient times, the northern peoples have had a legend about a mysterious island - a warm oasis where unprecedented animals and the mysterious Onkilon tribe live. Across the icy desert, a group of daredevils sets out in search of him and actually comes out onto land covered with forests and meadows, where mammoths and woolly rhinoceroses roam, and they are hunted by primitive people. “Plutonia.” Exploring one of the northern islands, the expedition of the ship "Polar Star" discovers that the Earth is hollow inside and there is life under the earth's crust, warmed by the luminary located in its center. Different eras coexist here: Pliocene, Miocene, Jurassic...Dinosaurs and pterodactyls, mastodons and saber-toothed cats, giant ants - the journey turns into a constant struggle for survival. Science fiction by Vladimir Obruchev is not only incredible adventures, but also a unique story about the past of the Earth .