Corisco is a small island of Equatorial Guinea, located 29 kilometres (18 mi) southwest of the Rio Muni estuary that defines the border with Gabon. Corisco, whose name derives from the Portuguese word for lightning, has an area of just 14 km2, and its highest point is 35 metres (115 ft) above sea level. During the Iron Age (50 BC - 1400 AD) and prior to the arrival of the Portuguese, the island was densely settled. The most important evidence of human occupation comes from the area of Nandá, near the eastern coast, where dozens of prehistoric burials have been excavated. After more than three centuries of abandonment, during which the island was sporadically visited by European sailors, Corisco was settled by the Benga people. They arrived during the second half of the 18th century attracted by the prospects of trade with the Europeans. The island was later acquired by Spain in 1843, as a result of an arrangement made by J. J. Lerena y Barry with Benga king Bonkoro I. Bonkoro I died in 1846 and was succeeded by his son Bonkoro II, but due to rivalries on the island, Bonkoro II moved to São Tomé, and Munga I ruled in Corisco 1848 to 1858, his son Munga II taking over, and meeting the explorer Manuel Iradier in the 1870s. In general the Spanish paid little attention to Corisco. In the early part of the 20th century it was part of the administration of Elobey, Annobon, and Corisco, and postage stamps were issued under that name. It became an integral part of Equatorial Guinea upon independence. Corisco and the surrounding waters of Corisco Bay have become of interest in recent years for their oil prospects.