This book will tell you about things far beyond the usual unresolved problems for science. Why are scientists and local historians with such inexhaustible perseverance looking for the legendary library of Ivan the Terrible or Sannikov Land? And "Tunguska Divo"? What exploded over the Siberian river in 1908: a comet, meteorite or spaceship from other worlds? The mysteries of the history of the crowned rulers of Russia are sometimes no less significant.