Sith temple (Mustafar)

A Sith temple once stood in Mustafar's Gahenn Plains. This planet's site was positioned above a cave that contained a locus of the dark side of the Force. By the time the Clone Wars occurred, the temple was no longer present, but its history was known to Sith Lord Darth Sidious, who operated a secret facility there. Later, Fortress Vader, the personal residence of his apprentice, Darth Vader, was erected where the ancient temple had been.