Arcturus Station is a 5-kilometer diameter Stanford Torus-type space station, at the trailing Lagrange point (L5) of the gas giant Themis. Construction on Arcturus Station began in 2151 and concluded in 2162, utilising many metal-rich asteroids that remain nearby, housing transient populations. Arcturus Station was inaugurated in 2156, and has served as the military and political headquarters of the Systems Alliance since the First Contact War. As the headquarters of the Alliance Navy, Arcturus Station is the command center of the fleet, and is conveniently located at the nexus of several mass relays. Furthermore, it guards the mass relay leading to Earth. Arcturus's centralized location makes it an ideal choke point for defense as well as a jumping-off point for further exploration.