Earth astronomers have discovered a class "M" planet. Discovery probes - sent to the planet - confirmed the presence of habitable atmosphere.
Moreover in the circumpolar regions has been found object - of extraterrestrial spacecraft. Near of it place, and was decided to create a planetary base.
But the most amazing discoveries have been waiting for them to come.
Infiltrating into object - turned out a alien - spaceship and go to its bottom (from the surface) levels, they have made a surprising discovery.
In some ancient times, this spaceship fell into surface or specially rammed into ice overlapping network of huge ice caves, which are hidden under the arches of ancient giant metropolis. Abandoned but not dead.