Year - 2300, the bombs fell.
Year - 2400, the remaining humans left the bunkers.
Year - 2600, the human race rebuilt their civilisation.
Year - 3000, the humans started to build new homes.
Year - 3500, The Cenotaph started being build.
Year - 5000, The Cenotaph was completed.
Built on the edge of the solar system far beyond Pluto sits The Cenotaph. The largest mega structure the humans ever created, the last hope of a real home for the remaining humans in the universe.
Mars, Venus, Mercury, Earth, their moons, everything left uninhabitable after the devastating wars that humans waged upon one another. Earth was lucky, the nuclear fallout was lower than the other planets but still devastated everything, the humans that left those bunkers never saw natural light before. The older humans passed down stories from the surface until it turned to legends.
They rebuilt society from the ashes, learned from mistakes, created a better future for the human race. It wasn't long before they looked upon the stars once more, they saw a new hope, a new home.
Over a thousand years of construction the Cenotaph was completed.
Year - 6583. The human race now solely exists within the Cenotaph, controlled by an AI known as Nebula. The AI was programmed to keep the human race alive, it accomplished this goal by maintaining sustainable amounts of food and water. Nebula provided all of the basic needs for human survival, it was a seemingly perfect world for humans but natural instinct within humans crept back into society.
Factions formed, Nebula let them do as they pleased unless it involved mass loss of life. One old faction once tried that, a renegade group with the idea that the human race should've gone extinct. Nebula had the group executed with less than a handful of members surviving, it set a harsh example that you do not interfere with Nebulas goal, no such attempt had ever been made since.
Corruption, murder, theft, war, terrorism, racism, sexism, they all exist within the Cenotaph but are relatively left untouched unless their actions threaten either Nebula or generate mass loss in short time.
The procurement of natural resources ceased when the Cenotaph took in what was left of humanity, luckily Nebula had the knowledge of the old civilisation. With this they developed autonomous ships to mine asteroids for vital resources, used refineries to create usable resources, all of this done by a growing army of construction bots controlled by Nebula. The Cenotaph was powered by colossal solar arrays that looked like an ocean as the blue tint reflected in the sunlight.
It was strange, so far into the future and yet it seemed so stuck in time from thousands of years ago.