The Pirran Caverns are a giant underground cave system, running the entire length of Deltora. The Caverns consists of three isles were the three different groups of Pirra settled down, after they were forced out of Pirra by the Shadow Lord. The Cavern are filled with water, forming an underground ocean, with the ceiling changing colour to reflect the gemstone of the tribe territory it is situated beneath.
Each Isle's people had a piece of the Pirran Pipe which was split due to trickery by the Shadow Lord. The Plumes had the mouthpiece of the flute, although it was stolen and eventually ended up with Glock. The Auron's had the middle stem, and the Keras had the endpiece.
The Barren Island is a small island located in the Opal caverns, which is also home to the island of Auron and-formerly-the Auron rafts. It is apparently without the plant life or fungus seen on the Pirran islands, and it's sole inhabitants are a species of large, carnivorous Grubs that feed upon Sea moles who end up on the island or any travelers unaware of the danger. The island is surrounded by brightly colored seaweed planted by the Aurons as a warning against danger.
The Auron Rafts were built by the Aurons who were exiled from their island when they refused to accept the illusory recreation of Pirra created by many of their fellows. Using materials from the island, they built the rafts, which served as their home for many centuries and were visited by Doran the Dragonlover. After the last of the islanders died and they were able to reclaim the island, it is unknown what became of the rafts; since they were no longer needed it seems likely that the Aurons would have disassembled them to put the material to other uses.