Welcome the most terrifying place in the world – at least to a Portuguese sailor in the early 1400s.

They called it Cape Bojador (pronounced BOO-jay-dur), a Portuguese rendering of the local name given it by area residents – which in turn comes from abu khatar, Arabic for “father of danger.”

It doesn’t look so scary or dangerous on the map – just a small bump in the African coast in what is now Western Sahara.

But the Cape’s true danger becomes apparent when you imagine that the year is 1434 and you are sailing a single 30-ton wooden fishing boat – with only one sail and a crew of about 20 – down the African coast. And then you look at this map of global wind patterns, with Cape Bojador marked by the green circle:

The channel between the African coast and the Canary Islands functions as a giant wind tunnel. For your small fishing boat, it would make for a quick trip – but remember, you also have to get back. And for a boat that small with only one sail, there was simply no way to fight against such strong winds to sail back to Portugal. A trip around Cape Bojador was doomed to be a one-way trip.

In the early 1400s, Prince Henry of Portugal was determined to find a way to sail beyond Cape Bojador, to discover and exploit whatever lay beyond. He founded the world’s first naval research school and laboratory at the far southern tip of Portugal, where seafarers looked for a way around.

Their solution was as clever as it was terrifying. They called their strategy volta do mar, meaning “turn of the sea.” Rather than fight the wind to sail up the African coast, captains would order their ships to sail far out into the Atlantic, where they could pick up more favorable winds.

Of course, it’s one thing to have this strategy in theory, quite another to be the one to put it into practice. That dubious honor fell to Gil Eanes (1395-1450s?), who set off from Portugal in the small fishing boat described above. The expedition passed Cape Bojador and traveled as far south as what is now Mauritania, where they picked some roses of a previously-unknown variety as proof they had succeeded in their mission. Then they used the volta do mar to return home.

Within 20 years, the Portuguese regularly traveled as far as modern Ghana, unfortunately bringing slaves back with them to sell all over the world. Within 50 years, Portuguese navigators had rounded the southern tip of Africa; within 120 years, they had reached Japan.