Paradis Island

Paradi (パラディ) is an island on which the three Walls, Maria, Rose, and Sheena, are located. The island is massive in size and is just off the coast of Marley, the refined society where Grisha Yeager hails from.

History
For an unspecified amount of time, Paradis was one of the many territories belonging to the Eldian Empire. The 145th King of the Fritz family, the ruling bloodline of Eldia, decided in the year 743 to move the capital of Eldia to Paradis and abandon the never-ending conflict between the eight Titan houses, leaving the mainland and allowing for the beginning of the Great Titan War. As Eldia lost more and more territory to the Marleyans, the minority bloodlines of the empire, the King gathered as many Eldians and members of the royal family as was possible before raising three walls around their last piece of undisputed territory. Some time after the raising of the walls, the new Marley government built a 30-meter border wall along the southern shore of the island to prevent the Titans from escaping to the ocean.

Trivia

 * If turned upside-down and mirrored, the territories of Marley and Paradis heavily resemble the real life continental territory of Africa and the island of Madagascar, respectively. Although no relationship between them has been confirmed.