- Author: Belpois, Jeremy
- Title: The underground castle
- Necklace: The steamer. Code Lyoko
- Place: Casale Monferrato
- Editor: Piemme
- Year: 2009
- Word:
- Key: Children's fiction
- Signatura: BELP
The super computers that have recently reactivated military transports Jeremy, Yumi, Ulrich and Odd within Lyoko, XANA a parallel digital world, an evil artificial intelligence that wants to control the real world. There, the four friends meet a girl even anti-virus, the only weapon against XANA. It's called Aelita and remembers almost nothing of her past. A past inextricably linked to Lyoko and its secrets...
Retitlings
The book was never published in English. The title shown is a translation.
In Italian, the book was published as "Il Castello Sotterrane."