TIL that Marajó, an island in the Amazon river delta, has an area of 49000 sq kms and is larger than countries like Switzerland and Belgium.

For reference, it's roughly the same size as Kyūshū, 2/3 of Tasmania, or 1/2 of Ireland. That might not sound like a big deal until you remember that it's a fluvial island, unlike those three.

Fun fact: from December to May, most of the island gets flooded. (It's "wet season" there.)