The prison held around fifty inmates in a single chamber, with no access points save for a single small tunnel, the "chute", sealed by a force field. The chute lead to an airlock on the exterior, where ships docked periodically to deposit food and new prisoners. The fact that the prison was in space was largely unknown to the inmates, most of whom believed that the prison was underground.
In 2373, USS Voyager senior officers Lieutenant Tom Paris and Ensign Harry Kim were sent to this facility after being falsely convicted of a bombing on Akritiri. They were eventually rescued by a team from Voyager, led by Captain Kathryn Janeway and Lieutenant Tuvok. (VOY: "The Chute")