The Observatory seems to have been a surveillance device built by the precursor "First Civilization" about eighty millenia ago. Its cavernous ante-chamber was built as a security measure, while its long corridors were used to store thousands of crystal blood vials containing the DNA of those whom the First Civ wished to spy on.
At the heart of the Observator was a large theater lined with seats. At the fore was a massive device like an armillary sphere with a crystal skull housed at its center. When loaded with a crystal vial containing a subject's blood, the observatory device would come to life, illuminating the room with a holographic projection of a real time feed from the subject's own eyes and ears. In this way, the First Civ could spy for an indefinite period on this subject and those with whom he or she was associated, without fear of detection.
Note too that the crystal skull can also be removed from its perch, turning it into a portable device, but also rendering the Observatory itself inoperable.
(Fantastic work, guys! We found it! We'll send this data to Laetitia and see what she comes up with. I have no doubt she'll want to send a team down there as soon as possible. Likely for those blood vials, as modern day surveillance systems are almost on par with that crystal skull device. - OG)