Guinea-Bissau
Early reports of Europeans reaching this area include those of the Venetian Alvise Cadamosto's voyage of 1455, the 1479–1480 voyage by Flemish-French trader Eustache de la Fosse, and Diogo Cão. In the 1480s this Portuguese explorer reached the Congo River and the lands of Bakongo, setting up the foundations of modern Angola, some 4200 km down the African coast from Guinea-Bissau.

Q: What country is about 4200 km from Guinea-Bissau?
Angola