Reminds me of René-Levasseur Island in Canada. It is a nearly circular island within a lake that's not much bigger than itself. And it, in turn, contains lakes, with islands within them.
I'll admit I had only really been looking into the oceans for places like this. I'm really enjoying reading about René-Levasseur Island, thank you for posting!
https://www.google.com/maps/place/Ren%C3%A9-Levasseur+Island...