Lake Roccaluce is a lake which is located right in the middle of the Magic Dimension in front of Alfea, Cloud Tower, and Red Fountain, not far from Magix City. The nymphs of Magix are said to live in its depths.
Water Nymphs' Village
The Undines live in the lake, near the Black Mud Swamp. They live in a village of air bubbles attached to water lilies. These bubbles are made of a special material that they make out of a plant called Xylith.
When the Ancestresses attacked Domino, Daphne tried using her Sirenix powers to fight the Witches but her powers turned against her because of the Witches' curse and turned her into a bodiless spirit, and she became bound to the cave where the Source of Sirenix is found.
After the Trix steal Bloom's Dragon Flame, Bloom goes to Domino where Daphne tells her that she was once the nymph of Lake Roccaluce. Later, after a failed attempt to retrieve the Dragon Flame from the Trix by sneaking into Cloud Tower, Bloom and Sky wander across the forests and, upon hearing Daphne's calling, Bloom goes to Lake Roccaluce where Bloom regains control of her powers after Daphne reveals to her that she still has the Dragon Flame in her.
In Season 3, Valtor uses the Spell of the Elements to flood Cloud Tower with Lake Roccaluce's waters and he used the caves from under the then dried lake as a trap for Bloom. When Bloom used her Fairy Dust to free all the spells he had stolen, Valtor called the Spell of the Elements, and involuntarily the water of Lake Roccaluce as well, back to him, seemingly drowning him, though he survived.
Tritannus later entered Lake Roccaluce after stealing the powers of Nissa, the Selkie who guards the Ocean Gate of Magix, and he captured Daphne in the hopes of knowing the secret of how to acquire Sirenix from her.
After the Trix attack Marion and Oritel, Daphne reveals to Tritannus that her Sirenix powers are protected by the Source of Sirenix found in Lake Roccaluce. Tritannus then goes to Daphne's cave in Lake Roccaluce and destroys the Source of Sirenix, causing the Lake to start drying up, and he then stole Daphne's Sirenix powers from her and gives them to the Trix. The Winx, after defeating a pollution monster created by Tritannus, combine their powers with those of the Selkies to restore the Source, which causes their Guardians of Sirenix to call upon Omnia, the Supreme Guardian of Sirenix, who gives Sirenix powers to the Winx, as they had completed their Sirenix Quest. From there, the Winx enter the Infinite Ocean.