Location from Pokémon HeartGold & SoulSilver by Game Freak / Nintendo
A treacherous island archipelago off the Johto coast, surrounded by whirlpools — and below the waterline, where Lugia sleeps in the deepest chamber, is exactly as far away as it chose to be.
The Whirl Islands exist as a barrier, not a destination — and Lugia chose them specifically. The whirlpools are natural features that make casual access impossible. HM Whirlpool (obtained from Lance after the Lake of Rage incident) is required. The cave system inside is designed to disorient. Lugia lives at the bottom. Not in the accessible sense of 'there is a boss room at the end' — in the sense that it went as deep as it could go and stayed there, because the power it carries makes even minor movement dangerous to the surface. In HGSS, the Silver Wing and the Kimono Girls' ceremony summon Lugia from the depths. The summoning is the game acknowledging that Lugia wouldn't come up otherwise. It takes effort, ritual, and something Lugia apparently recognizes as worth answering.
Four islands clustered together in the sea south of Olivine, each separated by whirlpools that require HM Whirlpool to pass. The caves inside are waterfilled and winding, the correct path downward not obvious. Deeper in, the water is colder and quieter. Then deeper still.
Also known as: Whirl Islands