Portuguese discovery of the sea route to India of the "São Gabriel" and its sister ship, the "São Rafael" that were used by Vasco da Gama to sail past the Cape of Good Hope and continue to India. One of the sailors, Bartolomeu Dias passed the southernmost point of Africa known as the Cape of Good Hope in 1488. He declared it possible to travel to India by going around Africa. The Portuguese were then able to make an immense profit by using their own ships to retrieve the spices. This global expedition was launched on 8 July 1497. It concluded two years later with the entry of
Portuguese discoveries tip of Africa, disproving the view that had existed since Ptolemy that the Indian Ocean was separate from the Atlantic. Also at this time, Pêro da Covilhã reached India via Egypt and Yemen, and visited Madagascar. He recommended further exploration of the southern route. As the Portuguese explored the coastlines of Africa, they left behind a series of padrões, stone crosses inscribed with the Portuguese coat of arms marking their claims, and built forts and trading posts. From these bases, the Portuguese engaged profitably in the slave and gold trades. Portugal enjoyed a virtual monopoly of the Atlantic slave trade