The author, one of the most outstanding Russian geologists, combines science fiction with authentic scientific fact in this amazing venture into the subterranean regions of the Pacific Arctic, undertaken by a stalwart expedition of Russian scientists. As the men probe the icy Arctic world, they soon become aware of their descent into a changing landscape with grass and trees and an overhanging peculiar red sun, which they call Pluto. The ""mountain"" they approach is an astounding gigantic mammoth, and the terrain they penetrate is filled with astonishing prehistoric creatures. Fascinated by their discovery of this inner planet, now dubbed Plutonia, they forge ahead to further startling perplexities which challenge the core of their knowledge and ingenuity but with which they manage to contend. This is a most erudite adventure tale buttressed by accurate geological, biological and botanical information, geared for the intelligent reader.