Harbor Three was a main shipyard of the Republic of Cinnabar, located in the harbor of the capital city of Xenos on the planet Cinnabar.
At the time of the Kostroma crisis, Admiral Koffe's heavy cruiser squadron reported to Harbor Three for refit. (RCN1)
Some time later, the captured Kostroman corvette Princess Cecile was refitted and readied for Costroman naval service in a bay next to the battleship Aristotle. (RCN2)