Lava Tube is a location in The Precursor Legacy. It is the only way to Gol and Maia's citadel, and as such is the second-to-last location in the game. It is a large underground network of molten lava, connecting Volcanic Crater to what used to be the Yellow Sage's hut, and has since been outfitted with metallic highways, dark eco factories, and other artificial structures.
After arriving at Volcanic Crater, Keira reveals to Jak and Daxter that they need to collect seventy-two power cells in total in order to upgrade the A-Grav Zoomer's heat shield to withstand the tube's 800-degree+ temperature. After crossing the tube and activating the respective warp gate, only Keira traveled through to meet Jak and Daxter, where she then reveals that her father, Samos, had been kidnapped by Gol and Maia. Jak and Daxter then traveled into the citadel.
Lava Tube is a large underground connection between the Red Sage and the Yellow Sage's huts. The factory inside the tube and the metal pathways are yet of unknown origin and purpose. The large "bowl-shaped" factory could have possibly been used to redirect or channel the tube and the crater's lava.
The tube is divided into three parts. The first part is a volcanic pass full of molten lava and slightly solidified cool spots, with large pathways. Here is where a secret path (see video) can be found. The next part is the factory which has multiple rotating orbs called power spheres that when destroyed open the door to the final part of the tube. This part is guarded by mines and has multiple rails transporting dark eco barrels, which destroy the zoomer on collision. The third part consists of large and complex metallic tracks, ending at the front door of the citadel.