Super Star Destroyer

The Super Star Destroyer is one of the largest, most powerful Imperial vessels ever created. It follows the same basic dagger-shaped design of the Imperial-class Star Destroyers, but magnified to much larger scale. A smooth hull presents an arrowhead shaped profile when viewed from above. Resting in the center of this hull is an "island" of habitable volume. Weapons emplacements bristle on the layered city-like surface. The trapezoidal command tower stands near the aft end of this island, capped with two geodesic communication and deflection domes. The underside is a busy network of engineering and superstructure. Thirteen colossal engine thrusters glow blood red as they push the immense craft through space. 
Though there are several command ships, the most distinguished of these Star Destroyers is Lord Vader's flagship, the Executor. This vessel led the Imperial Death Squadron after the Battle of Yavin. It also served as the command ship at the Battle of Endor. 
At that critical engagement, its officer, Admiral Piett, was tasked with preventing Alliance warships from escaping the battle. He did not expect the unorthodox Alliance strategy of engaging the Imperial Fleet at point-blank range. The Executor was a prime target for repeated barrages from Alliance vessels. Eventually, the Rebel ships were able to penetrate its powerful bridge shields. A wayward A-wing starfighter, crippled and out of control, spun directly into the Executor's bridge. Its control systems destroyed, the Executor was embraced by the second Death Star's gravity well, and the two collided in a colossal explosion that destroyed the flagship.