At first I was slightly disappointed by the definiton, but not anymore after scrolling through the list.
> Islands in lakes on islands in lakes on islands in lakes
> Moose Boulder was claimed to exist in the seasonal pond of Moose Flats on Ryan Island in Siskiwit Lake on Isle Royale in Lake Superior in the United States.[17] In 2020, an expedition to the island found that it is potentially a hoax, along with the aforementioned seasonal pond
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> Lakes on islands in lakes on islands in lakes
> Only one such lake is known
> 62°39′5.8″N 97°47′11.8″W
> There is, even further, an island in that lake, making it the only such island in the world that has been discovered so far.
> Islands in lakes on islands in lakes on islands in lakes
> Moose Boulder was claimed to exist in the seasonal pond of Moose Flats on Ryan Island in Siskiwit Lake on Isle Royale in Lake Superior in the United States.[17] In 2020, an expedition to the island found that it is potentially a hoax, along with the aforementioned seasonal pond
(...)
> Lakes on islands in lakes on islands in lakes
> Only one such lake is known
> 62°39′5.8″N 97°47′11.8″W
> There is, even further, an island in that lake, making it the only such island in the world that has been discovered so far.