Rura Penthe

Rura Penthe is a dilithium-rich asteroid used as a penal colony by the Klingon Empire. As the extremely low surface temperature of Rura Penthe makes it uninhabitable by most life forms, the mines are located underground.

Life in the penal colony is extremely harsh, with few prisoners surviving more than a year. Therefore, banishment to the mines of Rura Penthe is one of the most feared punishments throughout the galaxy, often said to be worse than death. The only known escapes from Rura Penthe are Earth Starfleet Captain Jonathan Archer in 2152, and Starfleet Captain James T. Kirk and Commander Leonard H. McCoy in 2293. (ENT episode: "Judgment" and TOS movie: Star Trek VI: The Undiscovered Country)