Arcology: A prominent feature, reaching up to several miles wide and high, of the Empire’s older and higher-population worlds, where clusters of several of them in lieu of sprawling suburbs (they’re also much easier to build than suburbs on non-garden worlds, for one thing, where the distinction between “arcology” and “habitat” blurs) around a relatively conventional downtown will form the cores of cities, interspersed with lesser buildings, estates, parks, and woodland.