A massive floating structure made of white bone-like material, Gaudium is guarded by four satellites which create a large bluish barrier to repel intruders, and armed with laser like weapons to destroy anything the circumvents this barrier.
Earl Tyrant sits in the throne room surrounded by his Lords of Gaudium and Makenshi. Close to the throne room is the heart of Gaudium, within which can be found Chaos itself. Gaudium is a maze-like structure with a complex network of rooms. Makenshi usually stays outside to be away from the other Lords of Gaudium. In the series climax, Gaudium was heavily damaged with Herba making it her base of operations.
- Chaos - Chaos's main body is hidden deep within the fortress, where it is fed by Oscha and the negative emotions of Wonderland.
- Earl Tyrant - the king of Gaudium, the Earl can be seen on the throne of the castle almost constantly, rarely seen leaving it.
- Fungus - Fungus can be seen here whenever he is not either searching for the protagonists or attacking them, and he returns here to rebuild his body whenever he is defeated.
- Herba - initially one of the Earl's lords, she resided here and left only to assail the protagonists. After Chaos was defeated and the other lords killed, she crowned herself queen of Gaudium and took it for herself.
- Makenshi - as the fifth lord of Gaudium Makenshi is seen within Gaudium often.
- Oscha - as caretaker of Chaos, Oscha remains here almost constantly.
- Pist Shaz XI - After the Earl accepts him as one of his lords, Pist spends a great deal of time within Gaudium, though this lessens towards the end of the series.
The track "Colossal Fortress Gaudium" (巨大要塞ガウディウム, Kyodai Yousai Gaudiumu?) is the location theme for Gaudium. It is the seventeenth track in the Final Fantasy: Unlimited - Music Adventure Verse 1 and is composed by Shirō Hamaguchi.
Gaudium is the Latin word for "joy." It is a play on words; it is here that Earl Tyrant spreads his version of joy to the world, but others see it as a place of terror and horror.