In 1488, he became the first European navigator to round the southern tip of Africa and to demonstrate that the most effective southward route for ships lies in the open ocean, well to the west of the African coast.

His family had a maritime background, and one of his ancestors, Dinis Dias, explored the African coast in the 1440s and discovered the Cap-Vert peninsula in today's Senegal in 1445.

[3] In 1481, Dias accompanied an expedition, led by Diogo de Azambuja, to construct a fortress and trading post called São Jorge da Mina in the Gulf of Guinea.

Dias was also charged with searching for Prester John, a legendary figure believed to be the powerful Christian ruler of a realm somewhere beyond Europe, possibly in the African interior.

[6][7] No contemporary documents detailing this historic voyage have been found, as almost all maritime records were destroyed in the 1755 Lisbon earthquake and ensuing tsunami.

Like his predecessor, Cão, Dias carried a set of padrões, carved stone pillars to mark his progress at significant landfalls.

Dias planned to drop them off at various points along the African coast so that they could testify to the grandeur of the Portuguese kingdom and make inquiries into the possible whereabouts of Prester John.

[9] The expedition sailed directly to the Congo and proceeded more carefully down the African coast, often naming notable geographic features after saints honored on the Catholic Church's calendar.

Whatever its cause, the change of course brought them success: the ships traced a broad arc around the tip of Africa and, on 4 February 1488, after 30 days on the open ocean, they reached the continent's southern cape and entered what would later become known as Mossel Bay.

Dias's expedition reached its furthest point on 12 March 1488, when it anchored at Kwaaihoek, near the mouth of the Boesmans River—where they erected the Padrão de São Gregório.

The ships made stops at Príncipe, the Rio do Resgate (in present-day Liberia), and the Portuguese trading post of São Jorge da Mina.

[16] Following Dias's return from his successful first voyage around Africa's southern cape, Portugal took a decade-long break from Indian Ocean exploration.