Boin Archipelago

The Boin Archipelago 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.

Geography
In that island, it is located 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. In the anime, this forest resembles a food-themed them park more than anything else. Although it's 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 first revealed to be a group of giant, seaborne carnivorous plants in anime episode 455. This was later revealed to be canon in manga chapter 591. The only difference is that the anime depicted the island's center as having teeth, while the manga shows the island as not having teeth.