Southern Cross

From Command and Conquer Wiki

Southern Cross was one of GDI's central command centers. In 2030 it was commanded by General Paul Cortez, who assumed authority over GDI forces following the loss of contact with Philadelphia and the base was used as a temporary global command. Furthermore, it contained at least one operational EVA unit which coordinated global communications while the Philadelphia was out of contact with Earth.

Southern Cross itself was surrounded by a network of defenses, and contained extremely powerful command and control computers capable of directing a Global War in real time.

Presumably, it was run over by Nod during the opening stages of the Third Tiberium War. GDI was able to eventually retake the base.