Seventy years later, and about fifty years before the Norman conquest of England, certain Persians settled at Kilwa in East Africa, led by Ali, who had been despised in his land because he was the son of a black Abyssinian slave mother. Kilwa, because of this, eventually became the most important commercial station on the East African coast, and in this and all these settlements a very large mulatto population grew up, so that very soon the whole settlement was indistinguishable in color from the Bantu. In 1330 Ibn Batuta visited Kilwa. He found an abundance of ivory and some gold and heard that the inhabitants of Kilwa had gained victories over the Zenji or Bantu. Kilwa had at that time three hundred mosques and was "built of handsome houses of stone and lime, and very lofty, with their windows like those of the Christians; in the same way it has streets, and these houses have got terraces, and the wood-work is with the masonry, with plenty of gardens, in which there are many fruit trees and much water."[32] Kilwa after a time captured Sofala, seizing it from Magadosho. Eventually Kilwa became mistress of the island of Zanzibar, of Mozambique, and of much other territory. The forty-third ruler of Kilwa after Ali was named Abraham, and he was ruling when the Portuguese arrived. The latter reported that these people cultivated rice and cocoa, built ships, and had considerable commerce with Asia. All the people, of whatever color, were Mohammedans, and the richer were clothed in gorgeous robes of silk and velvet. They traded with the inland Bantus and met numerous tribes, receiving gold, ivory, millet, rice, cattle, poultry, and honey. On the islands the Asiatics were independent, but on the main lands south of Kilwa the sheiks ruled only their own people, under the overlordship of the Bantus, to whom they were compelled to pay large tribute each year. Vasco da Gama doubled the Cape of Good Hope in 1497 and went north on the east coast as far as India. In the next ten years the Portuguese had occupied more than six different points on that coast, including Sofala.[33] Thus civilization waxed and waned in East Africa among prehistoric Negroes, Arab and Persian mulattoes on the coast, in the Zend or Zeng empire of Bantu Negroes, and later in the Bantu rule of the Monomotapa. And thus, too, among later throngs of the fiercer, warlike Bantu, the ancient culture of the land largely died. Yet something survived, and in the modern Bantu state, language, and industry can be found clear links that establish the essential identity of the absorbed peoples with the builders of Zymbabwe. So far we have traced the history of the lands into which the southward stream of invading Bantus turned, and have followed them to the Limpopo River. We turn now to the lands north from Lake Nyassa.