Krypton was a planet in the Rao system in orbit of a red sun. It was the notable home of Kryptonians, before the planet was destroyed in a seismic implosion due to careless mining of the planetary core. Prior to the implosion, Krypton endured the Kryptonian Civil War which resulted in the death of its foremost scientist Jor-El and the incarceration of General Zod and his Sword of Rao. Nearly all Kryptonians were killed in the implosion, except for Kal-El, Zod, and the Sword of Rao.
Krypton survived for 8.7 billion years. Kryptonian civilization evolved there and was over 100,000 years old, many millennia more advanced than human civilization on Earth. Their culture had begun exploring other galaxies 18,000 years ago and even set up colonial outposts on other planets. However, the Kryptonians abandoned their colonies and began genetic cultivation, artificially engineering newborns for pre-determined roles in society. As a result, the planet's resources became exhausted.
Krypton was doomed to destruction as a result of its inhabitants' careless mining of the planet's core, accelerating a forthcoming seismic implosion. Jor-El attempted to warn the Governing Council of their mistakes, but at the same time, General Zod attempted a coup d'état, starting the Kryptonian Civil War. Jor-El used the distraction to infuse the Growth Codex of Krypton into the cells of his son, in hopes of preserving the Kryptonian race, before sending his son to Earth. Enraged, General Zod, killed Jor-El, but was arrested by the Sapphire Guards shortly thereafter. He and his followers were then banished to the Phantom Zone for 300 years, shortly before the planet imploded in 1980, leading the Kryptonians to be endangered. This caused General Zod and his followers to be freed from the Phantom Zone thereafter due to the shockwave.
Krypton is portrayed as having had an Earth-like terrain composed of canyons and oceans. Its gravity was much greater than that of Earth, and its atmospheric composition differed to the extent of being unsuitable for humans. Krypton featured many cities that were towering metropolitan areas surrounded by walls and towers.