Kuiper Belt

The  was a belt of rocks beyond the orbit of Neptune in the Solar System. It was discovered by Earth astronomers in 1992. It was very old, and was composed of the rocks that didn't form into planets or moons.

The Fourth Doctor and Sarah Jane Smith visited a spacecraft that was stationed in the Kuiper Belt. (PROSE: Observer Effect)

It was situated around 53AU from Sol. Around Steven Taylor's time, tens of thousands of mining stations were set up across the belt, so that rather than looking up at stars, one would see the working furnaces of the mines. One of these stations was Grace Alone. (AUDIO: The First Wave)