From Gineipaedia, the Legend of Galactic Heroes wiki
Econiapolis was the largest (and only) city on the planet Econia, in the former Free Planets Alliance. Initially intended to be the center of the planet's Terraforming efforts, by 788 UC (479 IC / 3588 CE) Econiapolis' economy had become dependent on trade with the Alliance soldiers stationed at the nearby Econia Internment Camp.
Had the terraforming project gone according to plan, the city of Econiapolis would have been able to support a population upwards of one million: with the project stalled indefinitely, however, the population of Econia numbered only slightly more than 100,000 in 788 UC (479 IC / 3588 CE). A small town, Econia's economy was wholly dependent on the existence of the Econia Internment Camp and supporting the 3,600 Alliance soldiers and 55,400 Imperial prisoners stationed there. (SL: 'Planet POW Camp')