From Halopedia, the Halo wiki
Lisbon Station is an orbital research facility of the United Nations Space Command stationed near Installation 05. It was built after the Office of Naval Intelligence discovered the location of the installation during the end of the Human-Covenant War. As permanent settlements are often at risk on the surface of the ring, Lisbon Station serves as the UNSC's staging point for installation research and artifact recovery teams. The station is located beyond the range of Installation 05's automated defenses.
The pioneer groups of Lisbon Station traveled to the installation to collect data on Forerunner structures, including a megalith that became comprehensively studied. Local inscriptions documented by Lisbon scientists on this structure indicated that it was built to serve as a tribute to Warrior-Servants who died during the final siege of ecumene colonies by the prehistoric human civilization.
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