Moon

The Moon, named as such following the successful colonization of Luna, is the site of the Final Battle in Heaven Will Be Mine.

Description
The Moon is described as being a second Earth, and a city was built on the colony. The plant life, water, and breathable atmosphere are supplied by terraforming engines. Although this work makes it possible for Luna-Terra to venture outside her Ship-Self on the Moon, the atmosphere is still very thin, and the waterfalls on the Moon turn to vapor at the bottom, but this bottom point slowly inches forward over time as the atmosphere establishes itself. Where the reach of the terraforming engines end, the plant life burns up almost instantly and the land can still be considered Luna.

Gravity Well
The Lunar Gravity Well allows the Ship-Selves to operate in space without the Gravity of humanity. It is located on top of a tower on the south pole. It is described as being like a massive engine. Shortly before the Final Battle in a Celestial Mechanics run, Cradle's Graces and Celestial Mechanics strike a deal to open the Gravity Well, thus destabilizing it.

When the Gravity Well is opened, it chaotically draws in all matter and emits enormous amounts of energy.

In the Cradle's Graces ending, Pluto expands the Gravity Well's radius until humans cannot communicate with or recognize each other. This creates a clear alien race for humanity to fight against and satisfies Iapetus's Unified Culture theory.