The cave is gold with smaller tubes, which is their prison. There are also crystals, which amplify the screech of the Pandemonium Sprites. Inside the Golden Auditorium, there is a door which is supposed to be the way into the Pandemonium Cave as seen in the episode where Musa, Tecna and the Pixies run from the screeches of the Pandemonium Sprites.
In episode five, Selina summons the Pandemonium Sprites to attack the Winx in the Golden Auditorium. Musa, Tecna and the Pixies lured the Pandemonium Sprites to their own cave with a melody. Once inside, Musa sings We Are a Symphony. The two fairies gain their Bloomix and defeated them together.