Here, bioluminescent plants, such as Grue Clusters, guide the player through the caves' many passages. In this area one alien arch can be found leading to the Primary containment facility. In this area you can also find the fungal sample.
The entrance to this cave system is located embedded into a cliff, facing the Bulb Zone, below the largest Tree Mushroom. These caves also connect to one of the Bulb Zone Caves. This cave is particularly large and is made up of long, winding tunnels that lead to and from a large central cave found inside. The Cuddlefish egg can be found in a chamber close to the entrance of the cave. Exclusive to this cave are Coral Shell Plates, Large Lithium Deposits and a single Brain Coral, located close to the transition to the Bulb Zone Caves. Holefish and Shuttlebugs inhabit this cave system, but no eggs aside from the Cuddlefish egg can be found.
There are two cave systems here. Both are found inside the stem of the Giant Tree Mushroom. The first cave contains an entrance at the top and bottom of the Giant Tree Mushroom, with the upper part being populated by Spadefish. The bottom entrance is facing Northwest, near a Brain Coral. The upper entrance is facing Southeast. A second smaller cave can be found at the base of the Giant Tree Mushroom, towards the East, containing a Cuddlefish egg.