|Present day Earth|
|Location||2nd planet from the Sun|
Earth is a real-life planet on which almost all of Adventure Time takes place. The earth had gone through at least two major catastrophic events which are the Great Mushroom War and an unknown event which resulted in the disappearance of roughly a fifth of the Earth's original mass, leaving behind a cleanly cut crater. Earth is first seen in "The Real You." Additional areas that are not physically connected to the planet also interact with it, such as the Cloud Kingdom, the Nightosphere, the Crystal Dimension, Lumpy Space, and the Dead World.
While it was always known that Adventure Time takes place in a post-apocalyptic world, the fact that the series is set on Earth was not directly stated until "Holly Jolly Secrets Part II," in which Simon Petrikov (Ice King) mentions that he obtained his crown in Scandinavia, a real location on Earth.
In episode "Five Short Graybles," a holographic visual of Earth is seen rotating, much like a desk globe. It is also depicted with a scooped crust, as first seen in "The Real You." In "The Lich" you can see the Earth again, when the Enchiridion opens a map and Jake wish to enhance.
- Main article: Mushroom War
Adventure Time takes place on a post-apocalyptic Earth. This has been hinted at throughout the series. When Jake enhances the view of the universe provided by the Enchiridion, the solar system is shown with a possibly engorged sun and the planet Mercury missing.
At some point in time, a large portion of the Earth became missing. Although the reasons of how this occurred is unknown, in "I Remember You," the Ice King is shown to have a drawing of an intact Earth with a giant meteor heading towards it. However, this may also be referring to the asteroid in the episode "Wizard."
There are about four continents left on the planet Earth. The Land of Ooo is the only continent that has been shown so far. Since no other continent is seen or mentioned in the show, virtually nothing is known about them.
The Land of Ooo is the main setting of Adventure Time, and is the home of Finn and Jake, along with all of their friends and foes. It is divided into different kingdoms, but there are also many geographical areas not known to be part of any kingdom. About three other continents can be seen to still exist on Earth.
Despite the apocalyptic events in the past, there is a diverse range of life on the Earth. Many of its inhabitants are sentient and demonstrate varying degrees of intelligence. However, due to the war, most of the inhabitants on the Earth have undergone some form of mutation due to the radiation from the Great Mushroom War. Some were not even living things before mutation gave them sentience. In addition, many inorganic inhabitants live on the Earth, such as robots. Most inhabitants of Ooo speak English, but other languages, such as German and Korean, are still spoken by a few individuals.
Science and technology
A great amount of scientific and technological knowledge had been lost due to the Mushroom War. This is mentioned by Jake in "The New Frontier" when he claims that rockets have not been re-invented yet. However, general science appears to have gone forward dramatically. Examples of this include the ability to design and create life (such as the Earl of Lemongrab), genetic splicing and mutating (shown when Princess Bubbelgum prepares the ingredients for the perfect sandwich), and even an immortality elixir (used to bring long dead Candy People back to life).
Due to the Great Mushroom War, magic runs rampant across Earth, or at least just in Ooo. Merging magic with science seems to happen a lot though, and the two may go interchangeably with scientists, but not with spell-casters. However there is some evidence of magic existing previous to the war as evidenced by Ice King's crown magically changing him and the environment around him before the war started.