The voyage of Vasco da Gama around the Cape of Good Hope in 1498 marked the Portuguese entry into trade, politics, and society of the region. The Portuguese gained control of the Island of Mozambique and the port city of Sofala in the early 16th century, and by the 1530s, small groups of Portuguese traders and prospectors seeking gold penetrated the interior regions, where they set up garrisons and trading posts at Sena and Tete on the River Zambezi and tried to gain exclusive control over the gold trade.