A Hive City or simply a hive, is a massive arcology, or self-contained city, that is home to millions of human beings loyal to the Imperium of Man. Hive cities are often found in clusters on the densely populated urban planets known in the Imperial lexicon as Hive Worlds. Hive cities have been built up over thousands of Terran years, in many cases stretching back into the Dark Age of Technology long before the founding of the Imperium. Hive cities are layered constructions of rockcrete and adamantium, comprising thousands of residential and industrial blocks leveraged one atop the other, forming a massive, man-made mountain usually capped by a crown of great spires that stretch thousands of metres into the sky. In general, the higher up one goes in a hive city, the more wealthy and powerful the residents, until one reaches the hive's spires where the nobility live, work and play.
Conversely, the lowest levels of the hive, down below in the great tunnels that catacomb a hive's foundations even below the industrial and forge levels, lies the Underhive, a massive slum inhabited by violent gangs and vicious mutants who have never seen the light of their world's sun. Hive cities often exist in closely-spaced groups known as hive clusters and there can be several thousand hive cities on a single Hive World. These arcologies are largely economically self-sufficient, producing all the industry and processed foods needed by the tens of millions of people who call them home.
They are also crucial to the Imperium's survival as they produce most of the manufactured goods required by Mankind. As a result, each hive creates millions of metric tons of trash and industrial waste that is directly pumped out into the surrounding world's environment. Given the massive population of most Hive Worlds, this means that their surfaces are usually reduced to industrial wastelands covered in toxic deserts where nothing can live or grow save for the hardy mutants who call these "ash wastes" home and often raid the covered train-like transports that move passengers and cargo between hive clusters.
Hive Cities are worlds unto themselves where the populace has never seen the rest of their planet and concepts such as the ground and sky are completely alien. There are entire regions inside the hive city blocked off by the ruins of sections or layers that have collapsed or been built over. These ruined areas of the hive often hide treasures beyond price: archeotech hoards, ancient stores of advanced technology saved in caches on many Hive Worlds during the upheavals of the Age of Strife to preserve the technological wonders that existed during the Dark Age of Technology on many human worlds. A hive city is divided into a number of zones, moving in increasing order from the base of the arcology to its spires:
◾Outskirts - The Outskirts of a hive city are not as terrible a place to live as the Underhive, but the Outskirts carries its own terrible risks. There is, of course, no power of any kind beyond the few portable fusion or petroleum-driven generators the residents can provide and running water and a constant food supply or basic medical care is sporadic at best. The biggest problems are dealing with the toxic environment of the ash wastes that surround most hive cities and the constant threat of attack by the fearsome mutants of those wastes. Yet the people of the Outskirts are also free to live their lives outside the rigid confines of social class and Imperial decorum that constrains all the people of the hive cities, high-and-lowborn alike or the Hobbesian struggle of all-against-all that defines the short and brutal lives of most Underhivers. Though life is difficult and extremely dangerous for the intrepid souls who decided to live outside of the hive cities all together, their lives are still their own and they serve no masters but themselves.
◾Underhive - The Underhive is the region of a hive city where the poorest of the poor and those citizens of the hive city who have been exiled for committing crimes or for political reasons live. In the Underhive, there is no law save for that created by the gangs that rule this dark ghetto. The Underhive is a difficult place to live where the power was long before turned off by the hive city's authority and the only rule is that might makes right. All manner of crimes and atrocities go unpunished every day in the seething, violent anarchy of the Underhive. Working technology is the only real currency that matters in the Underhive and the recovery of the right equipment can transform a lowly ganger into the ruler of all he knows - until he is displaced by someone bigger, stronger, smarter or just possessed of a working Lascannon. The people of the Underhive rule through fear and shun those rich and working class alike, who live above them in the better levels of the hive.
