Luzon is the largest an most economically and politically important island in the Philippines and one of the three island groups in the country, with Visayas and Mindanao being the other two. Luzon as an island group includes the island of Luzon itself, plus the Batanes and Babuyan groups of islands to the north, and the main and outlying islands of Catanduanes, Marinduque, Masbate, Romblon, and Mindoro in the south. The island group of Palawan, which used to be a province belonging to an administrative region of Luzon, has been transferred to Region VI in the Visayas in 2005 (Palawan is still part of Southern Luzon). Luzon was once known in Chinese history as the "Lesser Song Empire" or Luzon Empire (traditional Chinese: 呂宋國; pinyin: Lǚsòng Guó). Her rulers were recognized as kings (王) and not merely chieftains. The first European explorers recorded it in their charts as Luçonia or Luçon and inhabitants were called Luçoes . Under Spain, Luzon also came to be known as the Nueva Castilla or the New Castile.