This was the first time since CE that there's something on a ring that wasn't for Flood containment. It was an underwater museum exhibit to preserve something of historical and cultural significance. In that tunnel you can see dark shapes at the murky lake bottom of the ruins outside illuminated by floodlights and those four sided tablet structures are Forerunner art, similar to ancient human cuneiform or clay tablets inscribed with records, literature, or codes but a lot more high tech.

gem

Goated level design