Frozen planetoid used by the
Klingons as a high-security prison camp.
The prison was located underground as the surface weather was inhospitable and unable to support life. The conditions on Rura Penthe meant that being inarcerated there was as good as a death sentence as many prisoners were forced to work under terrible conditions in the dilithium mines.
Captain Archer served a short time at Rura Penthe before being rescued by his crew.
Kirk and McCoy also served time on Rura Penthe, after being falsly accused of assasinating Chancellor Gorkon in 2293.
