Ecumenopolis

Ecumenopolis, meaning, literally, "City Planet", is a form of Setting Aesthetics where... well, the name says it all: you have an entire planet that has been built over and subsumed into masses upon masses of infrastructure, creating the ultimate city that can reach from the towering peaks of mountain-sized skyscrapers down to an Underdark of maintenance tunnels, sewers, subways and long-buried layers of older cities. It's an idea mostly explored in Science Fiction, since that tends to lend itself more readily to the idea of people being able to literally build over an entire planet and not kill themselves in the process, but it also shows up in Science Fantasy or even post-apocalyptic Sword & Sorcery.

/tg/ Examples

• Cybertron, from the Transformers universe
• Terra (and lesser Hive Worlds), from Warhammer 40,000
• Coruscant, from Star Wars
• Ravnica, from Magic: The Gathering
• Trantor, from Isaac Asimov's Foundation series