Today, much of what I.A. Efremov (1907-1972) - a famous Soviet science fiction writer, man of encyclopedic knowledge, philosopher, paleontologist, historian - in his Siberian stories no longer seems as fantastic as it seemed to his first readers. So since the first publication of "Lakes of Mountain Spirits," for example, a mercury deposit has really been discovered in Altai. It was in the place where the events unfolded in the story "Diamond Pipe › geologists found a diamond deposit in Yakutia. The discovery of the Kapova Cave in Bashkiria confirmed the writer's hypothesis about the existence of a cave with drawings of African animals (the story "Golets Podlunny") and so on.