…When he said the World was round (or rather, they didn’t).
Christopher Columbus was born in the town of Genova, in what is now North-West Italy. The adjacent towns are happy to share the credit:
It is (or at least was) a popular myth that the accepted wisdom at the time was that the Earth was flat, until Columbus sailed west with the intention of reaching China, and bumped into the American continent on the way. In fact the Greeks had believed the Earth to be roughly spherical about 2000 years earlier, and had made an estimate of the Earth’s radius, based on the length of mid-day shadows at different latitudes. This knowledge had been preserved, and would have been well known to educated people of the era of Columbus (see Wikipedia’s Spherical Earth article for more details).
How widespread this knowledge was amongst the general populace is open to debate, but there is at least some evidence that it was known outside the world of the literate. for instance from the Wikipedia article:
the Elucidarium of Honorius Augustodunensis (c. 1120), an important manual for the instruction of lesser clergy, which was translated into Middle English, Old French, Middle High German, Old Russian, Middle Dutch, Old Norse, Icelandic, Spanish, and several Italian dialects, explicitly refers to a spherical Earth. Likewise, the fact that Bertold von Regensburg (mid-13th century) used the spherical Earth as a sermonic illustration shows that he could assume this knowledge among his congregation. The sermon was held in the vernacular German, and thus was not intended for a learned audience.