What is the diameter of the Halo ring Installation 04 in the Halo game universe?

The Halo ring Installation 04 has a diameter of 10,000 kilometers.

Installation 04 is one of the ring-shaped superweapons built by the Forerunners. Its enormous circumference provides room for an artificial atmosphere, terrain, oceans, and ecosystems that resemble a planetary environment. Despite its relatively narrow width compared with its full circumference, the ring supports a wide range of life.

The first Halo game takes place primarily on Installation 04, which the UNSC initially identifies as a mysterious alien structure. The ring is ultimately destroyed when Master Chief and Cortana trigger the Pillar of Autumn’s fusion reactors, preventing the Flood from escaping and stopping the installation from firing.

The diameter is sometimes confused with the ring’s circumference or width. A 10,000-kilometer diameter describes the distance across the circular structure, not the length of its outer surface. Other Halo installations share the same general megastructure design.