Dead Earth, transformed into a massive installation by a highly advanced civilization that came many thousands of years after humanity became extinct, along with all life on Earth. The aliens who took over the planet regard it with much reverence, believing it was the cradle of their civilization. Therefore, along with it a massive disc was built around, where an artificial terrestrial environment was cultivated on its surface for habitation, as well as to facilitate research on the many ruins that are found on the planet surface. The entire installation is capable of moving by its own power and can even travel through hyperspace. Since hyperspacial travels for such a colossal object requires a huge amount of energy, such operation requires the assistance of another ring-like support installation which is stationed around its vicinity.A big shout out to for the suggestion!!! Do check out his awesome gallery as well!