And Isle Royale which is currently closed for the winter. The park is free to enter two days a season but that wouldn't include the $136 ferry ticket (unless you take your own boat).
> Siskiwit Lake is the largest lake on the island. ... Siskiwit Lake contains several islands, including Ryan Island, the largest, which contains Moose Flats, a seasonal pond, which contains Moose Boulder. When Moose Flats is a pond, Moose Boulder becomes the largest island in the largest lake on the largest island in the largest lake on the largest island in the largest lake in the world.
> Siskiwit Lake is the largest lake on the island. ... Siskiwit Lake contains several islands, including Ryan Island, the largest, which contains Moose Flats, a seasonal pond, which contains Moose Boulder. When Moose Flats is a pond, Moose Boulder becomes the largest island in the largest lake on the largest island in the largest lake on the largest island in the largest lake in the world.
~ https://en.wikipedia.org/wiki/Isle_Royale
(Emphasis added.)