From Gineipaedia, the Legend of Galactic Heroes wiki
Econia (Japanese: エコニア) is a planet located in the Thanatos Starzone inside the former Free Planets Alliance. Originally unsuitable for human life, Econia was terraformed: the process was never completed, however. Despite the creation of a nitrogen-oxygen atmosphere by 788 UC (479 IC / 3588 CE), the planet was never fully forested. Only the area surrounding the lone city of Econiapolis held enough vegetation to support a human population.