Task: Question Generation
Input (English): The first Europeans to disembark and explore the region were the Portuguese navigators Diogo Cão in 1485 and Bartolomeu Dias in 1486; still the region was not claimed by the Portuguese crown. However, like most of Sub-Saharan Africa, Namibia was not extensively explored by Europeans until the 19th century, when traders and settlers arrived, principally from Germany and Sweden. In the late 19th century Dorsland trekkers crossed the area on their way from the Transvaal to Angola. Some of them settled in Namibia instead of continuing their journey.
Output (English): When did Bartolomeu Dias explore Namibia?