The Segmentum Solar is the vast region of Imperial space centred on Terra and the Sol System. The Imperial Navy shipyards for the Segmentum are located on Luna, and the Imperial Navy headquarters in the Segmentum is based within Mars' Ring of Iron. The Segmentum Solar is the central hub of the Imperium of Man and the most ancient and densely settled region of human space. Centered on Terra, where the Emperor of Mankind sits upon his Golden Throne, the central Segmentum is protected on four sides by the other Segmentae Majoris. The Battlefleet Solar of the Imperial Navy is the largest of the Segmentae fleets and is based in the orbital fleet docks of the so-called Ring of Iron that surrounds the Adeptus Mechanicus' primary Forge World of Mars.