Sarthong V was the inhabited fifth planet in its system. The planet was home to impressive archaeological ruins which were off-limits to outsiders.
Vash considered a visit to Sarthong V in 2366 after parting company with Jean-Luc Picard on Risa. (TNG: "Captain's Holiday") Despite his warnings about the manner in which Sarthongians treated trespassers, Vash did make the trip to the planet and was able to return with several impressive artifacts. (TNG: "Qpid")
This planet was only mentioned in dialogue.