The Longdan (竜胆/龍蛋, Rindou, lit. Gentiana or Dragon Egg) is pyramid-shaped land-cruising mobile fortress controlled by the Chinese Federation, capable of deploying dozens of Gun-Ru Knightmares. It has two large cannons and thirteen smaller cannons. Certain models are equipped with tank treads for land mobility, while others have hover systems to levitate across bodies of water. The Longdan's large cannons are comparable with the real-world Schwerer Gustav guns, which were used by Nazi Germany during the Second World War.