The home world of the Grogs and a former Kzinti colony. Conquered by Humans in 2425.

Down orbits L5-1668 (a corruption of BD+05 1668 (a.k.a. LHS 33), another name for Luyten's Star) , a faint, cool M-type star, significantly redder and cooler than Sol and 12.3 light-years from it. Down is made habitable in part because of its large moon, Sheila.

Grogs, though friendly, are feared by humanity, due to their telepathic ability to control the minds of animals (and possibly sentient species as well). Because of this fear, humans have placed a Bussard ramjet field generator in close orbit around Down's sun, thus enabling them to destroy the Grog population should they ever take hostile action against any sentient species.

Sources and references: The Handicapped, Grendel, The Heroic Myth of Lt. Nora Argamentine, Ringworld Engineers,

Other sites: Known Space Concordance, Larry Niven Wikia,