Cropped for size from the image at the via.
Reposted from 2020 to add some interesting material from The Fourth Part of the World, by Toby Lester:
"Thanks in large part to the labors of Arab astronomers and mathematicians, ancient Greek proofs of the earth as spherical had survived into the Middle Ages and were circulating in Europe... For centuries afterward the work would be taught and studied in schools and universities around Europe. 'If the earth were flat from east to west,' Sacrobosco wrote, 'the stars would rise as soon for Westerners as for Orientals, which is false. Also, if the earth were flat from north to south and vice versa, the stars that were always visible to anyone would continue to be so wherever he went, which is false. But it seems flat to human sight because it is so extensive.' Sailors certainly knew the world was round: a lookout at the top of a ship’s mast, Sacrobosco pointed out, always catches sight of land before a lookout standing at the foot of the mast -- 'and there is no other explanation of this thing,' Sacrobosco wrote, 'than the bulge of water.'"
Or see Ptolemy's third projection (1525):
For more regarding the modern "flat earth" hypothesis, see Kolo Jezdec's links in the Comment thread. Personally, I think a lot of the "flat earth" stuff online is just people messing around trying to be funny (cf Drabkikkers link to Birds Aren't Real). Although there are some really, really stupid people like the truck driver above.
Related: Falling off the earth nonsense
A couple other interesting excerpts from the book:
"Matthew [Paris, 13th century] drew his maps as a series of destination cities for pilgrims, often separated by the French word journee - meaning "day," as in a day's travel, a usage that gave rise to the English word journey...""The conquests led by Temüjin were legendary, and to celebrate them the Mongols posthumously bestowed on him the title Fierce Ruler, or Chingis Khan. Today, thanks to an imperfect Arabic transliteration of that name, he is widely known as Genghis Khan..."During the next four years, between 1237 and 1241, the Mongols swept through much of Russia, Poland, and Hungary, destroying entire cities, armies, and populations. After a rout in Silesia, one chronicler reported that Mongol soldiers had collected nine sacks full of their victim's ears and had sent them back to their capital, Karakorum, in the Mongolian steppe, as proof of their victory."