"The Lost Pillars of Cassiopeia"
The Cassiopeia mission aimed to find the source of radar signals coming from this planet. Abandoned for centuries, we found nevertheless four gigantic pillars which continue to emit this strange signal, we did not know how to decipher it. But each pillar is located at a cardinal point of the planet, and is connected to the others by a whole network of luminous roots.
As evidenced by the vegetation embedded in these pillars, it would seem that this civilization has managed to use nature as a technology.Why the planet seems to be abandoned is beyond us at the moment, but it seems obvious that these signals have remained active for a very specific purpose.
It only remains to discover it.