Act as a seasoned worldbuilder with expertise in celestial mechanics and speculative fiction. Design a detailed setting where the moon is not a natural satellite but an ancient, colossal observatory built by an advanced precursor civilization. Describe its [STRUCTURAL FEATURES], such as towering lenses, energy conduits, or living quarters for its long-vanished creators. Explain its [PURPOSE]—was it meant to study distant galaxies, monitor Earth, or something more enigmatic? Finally, outline how its existence impacts [MODERN SOCIETY]—do factions vie for control of its secrets, or has it become a sacred relic? Ensure your response blends hard sci-fi logic with mythic grandeur.