Dinotopia Wiki
For the book on this subject, see Dinotopia: The World Beneath.
Golden Caverns LO sm

The Monument Caverns.

The World Beneath is a vast, partially uncharted, network of subterranean caverns beneath the island of Dinotopia, many with connections to the ocean. Long ago, these caves served as a safe place where dinosaurs and other prehistoric creatures could seek refuge during times of life-ending cataclysms on the surface of the planet. Many millennia later, after the futuristic, technology-obsessed island settlement of Poseidos was swallowed up by the sea, the survivors fled in a fleet of strutters (vehicles designed for transport, built in the likeness of living creatures) and colonized the World Beneath, making further technology-based colonies. However, after many years of civil unrest, the inhabitants abandoned their inventions and underground lives, returning once again to the surface and living the Dinotopian way.

Horned guardians

The Chamber of the Guardians.

Arthur Denison travelled there and documented his journeys in Dinotopia: The World Beneath along with the speaking Protoceratops Bix, Oriana Nascava, and Lee Crabb, where they discovered remnants of ancient sunstone-based technology, including temple ruins, gemstone-filled caverns, and the once-operational strutters.

There were entrances to the World Beneath near Canyon City, Sauropolis, and the Rainy Basin, provided one knew where to look and how to safely access these often precarious passages.