Millennium Gate

The Millennium Gate as seen from space

The Millennium Gate was a 21st century structure, and Earth's first self-sustaining civic environment.

Built in the state of Indiana in the nation United States, its construction was complete around 2012.

One kilometer high, with a base of 3.2 kilometers, this structure could be seen from space.

Covered in highly-reflective solar panels, the Gate was a self-contained biosphere, even processing its own ecosystem.
Equipped with over six-hundred stores, this feat of architecture served as the model for Mars' first Earth colony.