Comporellon, originally Baleyworld, was a planet near Gaia and Sayshell that was renowned for its particularly old age. It was founded by the second wave of space colonists, known as the Settlers, and thus had a very superstitious attitude toward the first wave, the Spacers. They were also superstitious about Earth.
Golan Trevize, Janov Pelorat, and Bliss visit Comporellon in Foundation and Earth, and acquire the coordinates of three Spacer worlds: Solaria, Aurora, and Melpomenia from a historian.