Great Mother Planet

The Great Mother Planet (also known as Planet Promethium and Planet La Andromeda) is the capital of the Machine Empire, with the current queen Promethium leaving her home world La Metal as the area to get mechanized.

Appearance and Features
Whether Planet Promethium was an artificial planet or a natural one is unknown as the entire planet is a large city that can be seen from both space and in its sky. The planet features a ring like Saturn's and is slightly larger than Pluto.

The planet features a defense system to prevent intruders and illegal immigrants from getting in, especially if they are of regular flesh-and-blood. The weapons include plasma discharge gear that can destroy many ships. As such Galaxy Express trains must travel through a shielded express tube. Other obstacles are different depending on the medium including a black hole near the vicinity in the TV version or meteorites in the novel versions.