The Whirl Islands are a small archipelago located between the mainland of Johto and Cianwood City, on Route 41. Beneath the sea, a maze of dark caves sprawl, with explorers able to travel between the four islands with some amount of difficulty. Deep within these caves, Lugia can be found once the player has obtained the Silver Wing and Tidal Bell.
Named after the dangerous whirlpools that surround them, some parts of the Whirl Islands are mysterious and largely inaccessible. Children in Olivine City are told that bad kids are sent to the islands.
As explained in Pokémon SoulSilver, the Whirl Islands used to be one large island. At some point in time, there were two countries fighting over the island. Lugia, the guardian of the island, got upset and cast lightning bolts to tear the island into four pieces. It then disappeared into the deep end of the waterfall basin, longing for the invisible trust between people and Pokémon to manifest once more