Chi was a planet in the Delta Quadrant and the homeworld of the Chiar. It was extremely heavily populated and built up, with little in the way of a natural environment except for nature reserves. Due to a civil war, half the continents on the planet were cordoned off with high-intensity microwave barriers, designed to prevent the imprisoned losing faction from exiting, as the microwave field would destroy any nanites it came into contact with. (VOY novel: The Nanotech War)