The Arrun Labyrinth was massive garden created by the Kingdom of Arrun some time prior to its collapse approximately 500 years before the arrival of the Japan Self-Defense Forces in the Special Region. The Labyrinth is surrounded by a massive forest, presumably irrigated by some means, given that it is surrounded by the semi-arid regions on the edge of the Western Deserts.
The Labyrinth itself consists of a maze of stone structures and corridors, which, which were, in its heyday, lined with various plants, including medicinal herbs. In the outer area of the labyrinth there is a building formerly used to store medicinal plants for shipping. The Labyrinth also contains a network of underground passages, possibly irrigation tunnels. The gardens are centered around a large tree.
Yōji Itami was the first person from Earth to explore the Labyrinth, going there in search of a Rokude Pear to cure Lelei's case of the Crety Epidemic before she died and was reanimated into a zombie-like state. Itami, accompanied by Rory Mercury and Yao Ro Dushi, found the labyrinth infested with undead victims of Crety Epidemic, as well as dangerous animals such as Cockatrices and Minotaurs.