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, a sentence to the mines of Rura Penthe is one of the most feared punishments throughout the galaxy, often said to be worse than death. The penal colony has no stockade, guard tower or electronic frontier. It only has a magnetic shield that extends over a significant part of the planet's surface, preventing beaming. The most common form of punishment given to prisoners is banishment to the freezing surface, where they don't survive for long.

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)