Ruins

Ruins are a new section of the world, coming in a future update, confirmed by Klei to be a second level of the caves. A prefab file titled "stairs" suggests the ruins will have a manmade (or thingmade) entrance. Objects found in the files associated with the Ruins are Relics, Rubble, and Ruins Statues. Nothing more is known at the moment.

Trivia

 * The Slurper was originally intended to live in the Ruins. Since the release of the Ruins had to be pushed back, the Slurper was made able to spawn in regular caves.

Pictures found in the game files
These are the pictures found in the game files: