The Dungeon (ダンジョン) is a complex labyrinth located under the Babel. Orario is the only place in the world that has a Dungeon and many people of different races gather from across the world to explore the Dungeon.
Before the Gods and Goddesses came down to the lower world, heroes fought againstMonsters with the help of Spirits. Once the Gods began to come to the lower world, the Gods bestowed the Falna upon them and gave them a status to better fight monsters. Ouranos was the first God to bestow a falna upon a person.
The Dungeon is seemingly alive, spawning monsters from walls and ceilings and repairing itself on its own. It has an immense hatred of the Gods, immediately sealing the exits of a room if it detects one, and spawns a black version of a monster in order to kill them. The black monsters are far stronger than normal and display some intelligence, as the Black Wyvern looked around for its target. Despite this, it doesn't spawn another black monster after the first one is killed even if the God in question isn't dead, implying that its ability to act is limited to some extent.
The dungeon is vast with the floors becoming progressive larger the deeper it gets. It takes at least five days for a party to reach the 50th floor. While the upper floors can be soloed or done with a pair, starting from the middle floors one must create a party or risk death.
The Xenos refer to the Dungeon as their mother and believe it created the Hidden Villages to protect them.