An island, in a lake, on an island, in a lake, on an island

On Luzon in the Philippines sits Lake Taal, which contains Volcano Island. Volcano Island itself holds a crater lake called Main Crater Lake, and inside that lake sits Vulcan Point — a small islet that is, in full, an island within a lake within an island within a lake within an island. It's recognised as the largest such recursive formation on Earth.

— Wikipedia contributors, drawing on Philippine Institute of Volcanology and Seismology records, Taal Volcano Main Crater Lake — Batangas, Philippines