Boin Archipelago

The Boin Archipelago (ボーイン列島, Bōin Rettō, called the Bowin Islands in the Viz Manga and FUNimation subs) is a series of flower shaped islands in the Grand Line. Within them are various gigantic bugs and vicious man eating plants. Usopp landed on one of these islands after being sent flying away by Bartholomew Kuma. It is said that anyone who enters this island has no chance of leaving it again.

In that island, the swindling forest of Greenstone (グリンストン, Gurinsuton, called Glinston in the FUNimation subs). Also, as of recent chapters, it is known to have a forest made of food, called the Forest of Gluttony, that includes a river of noodles surrounded by Plum Trees and Corn Stalks. Although, its mentioned there are thieves in Greenstone, the only known resident so far is Heracles.

The islands are actually giant carnivorous plants scientifically known as "Stomach Baron", that eat overweight animals that are in the Greenstone forest.

Anime and Manga Differences
The Boin Archipelago is revealed to be a group giant carnivorous plants in the Anime before the manga. This was revealed to be canon to the manga in Chapter 591.