The Caliban Caves is a cave system under the North West end of the Isle of Berk. It is connected to the Dragon Nursery which opens up onto Wild Dragon Cliff. It also opens up underneath the sea below into a giant cavern with air. Some of the tunnels are small, but can open up into gigantic caverns.
|“||The cavern had some interesting rock formations ... the weird shapes of fossilized dragon were caught in the stone. Some of them were very unusual, extinct species.||”|
|— Book 2|
According to Stoick, the cliffs drops very deeply into the water in front of the caves underwater.
|“||And Stoick knew that this particular part of the ocean, despite being so close to the cliffs, was very, very deep, too deep even for lobster pots.||”|
|— Book 2|
It is here that the Lucky Thirteen sank, and remains.
As told in How to Be a Pirate and How to Break a Dragon's Heart, after the fall of the Kingdom of the Wilderwest, King Grimbeard the Ghastly buried a tiny amount of his treasure in a chest on the Isle of the Skullions, and the rest of his treasure underneath the Caliban Caves. Grimbeard placed a baby Monstrous Strangulator here intending for him to grow into a fearsome guardian of the treasure. Grimbeard intended for his true heir to find the treasure as well as his favorite sword.
Around a hundred years, Hiccup Horrendous Haddock III, Fishlegs No-Name, Toothless, and Alvin the Treacherous arrived here after sinking to the bottom of the sea during the Battle of the Lucky Thirteen. Toothless sniffed out the true treasure and a swordfight between Hiccup and Alvin broke out. The Monstrous Strangulator emerged and devoured Alvin, but before he could devour Hiccup, he tricked the Monstrous Strangulator into killing himself. Hiccup, Fishlegs, and Toothless then escaped the Caliban Caves using Toothless' underwater breathing.
Alvin then turned out to be alive and cut himself out of the Monstrous Strangulators stomach with the Stormblade. Having no dragons to escape the Caliban Caves, Alvin was forced to walk through them for months to get to the surface of Berk.
Alvin tells the story of how he survived and left the Caliban Caves after the events of Book 2.
|“||... so I had no choice but to go through the Caliban Caves. THREE WHOLE MONTHS it took me, creeping through the darkness, eating little cavern dragons raw, licking the walls for water ...||”|
|— Alvin in Book 3|
|The Barbaric Archipelago of|
|Locations of the Isle of Berk and the Meathead Islands|