I once read an excellent essay by Umberto Eco that demonstrated quite well that the myth is not that of a flat earth but that of people believing in a flat earth. People, generally, from the ancient times have believed the earth was round. Ovid was one of them:
Sic ubi dispositam quisquis fuit ille deorum
congeriem secuit sectamque in membra coegit,
principio terram, ne non aequalis ab omni
parte foret, magni speciem glomeravit in orbis. (Metamorphoses 1.32-35)
Which is to say:
Thus, when whoever of the gods this was
had divided the chaotic mass and gathered it into members,
first, so that it might not be unequal in every
part, he formed the earth into a great ball.
Or, in Golding’s version of 1567, more poetic than mine by far:
Now when he in this foresaid wise (what God so ere he was)
Had broke and into members put this rude confused masse,
Then first bicause in every part, the earth should equall bee,
He made it like a mighty ball, in compasse as we see.
So there. The earth is round, and Ovid knew it.