There was an "overwhelming" agreement that the earth was flat because you were ostracised by the church and state if you said otherwise. Fucking idiots.
I don't even think that's true? The medieval view of the universe included a round Earth, since they were taking that model from the Greeks.
There's a whole deliberate mythology created around Christopher Columbus (I forget the name of the book that created it, but it's American) that he's the first American hero because he proved the world was round. He didn't, he was just trying to find a shorter route to India.