Castra is a planetary system in the United Empire of Earth (UEE). Discovered in SEY 2544, it was originally designated as a military staging area due to its jump point connection with the Oya system in the former Perry Line. At the end of the Messer Era, the system was opened up to non-military settlement and has since become a center of trade and tourism. The second planet from its sun, Cascom (Castra II), is expected to apply for representation in the UEE Senate in the near future.