Do you see this lake? It's Yathkyed Lake in northern Canada.

There are several islands in the lake. The largest island has its own lake.

That lake has several islands. One of those islands has a lake in it.

And that lake, as this photo provided by Ian Cameron of the Royal Meterological Society illustrates, has an island on it. It's a very small island (I'd guess it's at most 5 feet across), but it's an island.

That unnamed island is the only fifth-order island in the world.

We don't yet know of anyone who has visited there. I'd suggest it as a lair for a supervillain with a limited budget.