A hive city or simply a hive, is a massive arcology, or fully self-contained city, that is home to millions or even billions of humans. Hive cities are often found in clusters on the densely populated urban planets known in the official Imperial lexicon as Hive Worlds. Hive cities have been built up over thousands years, in many cases stretching back into the age of technology. 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 city's 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 countless number 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. 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. Their population is so dense that frequently the entire surface of the world is covered with the enormous hive cities streching from horizon to horizon

*Year 2075. A cyberpunk world. This is a world where all the nations of the world have unified, transforming the continents into massive and colossal cyberpunk cities the size of the continents. The name of planet Earth was changed to Titan. Furthermore, with advances in technology, we built other city-continents outside of Earth/Titan, or even inside the planet. The planets of the solar system had their names changed to those of deities, such as Jupiter=Zeus, Neptune=Poseidon, Mars=Ares, etc. The city-continents are: Europe became Aether, South and Central America became Asteria, North America became Astrea, Africa became Dantalion, Asia became Eos, Euro-Asia became Hyperion, Oceania became Aegaeon, Antarctica became Hygea. The other city-continents are: (In the Pacific Ocean, Atlantis originated. In the "Underworld" of the planet, Sheol originated. Above the clouds, Babylon originated. Submerged in the ocean, they created Sallos. On Mars/Ares, Gehenna originated. A city-continent that serves for communication with other races, originated in space, Nexus. In Neptune/Poseidon, Leviathan originated. As can be seen in the previous information, humans live in these city-continents with other races, which came from other systems in our galaxy or beyond.*