The Caves of Jotunn are a network of natural caves underneath the Isle of Berk. However, in the events of Underworld, they are greatly expanded on and mined by Captain Fiske and his crew, in order to destroy Berk.
The caves are large enough for dragons to fly through, and has an underwater portion that connects to the sea on the coast of Berk.
- The Jotunn are a group of god-like giants in Norse Mythology.
- In the Comic, the "o" on "Jotunn" has Umlaut marks above it.