In 1500, the Maore sultanate was established on the island. In 1503, Mayotte was observed and named (firstly "Espirito Santo") by Portuguese explorers, but not colonized. The island has known several eras of wealth (especially during the 11th century at Acoua or between 9th and 12th centuries at Dembéni), being an important part of the Swahili coast culture. However, its sister island Anjouan was preferred by international traders due to its better suitability to large boats, and, for a long time, Mayotte remained poorly developed compared to the three other Comoros islands, often being targeted by pirates and Malagasy or Comorian raids.