Like all Kathol technology, the launch gates were organic in origin, and took centuries to construct, or rather, to grow. In their completed form, they were massive disks, slightly concave, with eight tall towers spaced around their circumference, each one large enough to land a Star Destroyer on. These served to direct immense energies, opening a passage into hyperspace for colony craft.
Originally there were two launch gates, but during the days of the Old Republic, one of the launch gates was overloaded and destroyed when a Dark Jedi tried to conquer the system. The resulting energy surge, known as the Rift Disaster, created the Kathol Rift, and probably rendered the remaining launch gate inoperable; nevertheless, the second device remained largely intact in orbit around Kathol until after the Battle of Endor.