Eratosthenes of Cyrene proved that the earth was round and even accurately computed it's circumference prior to his death in 194 B.C.
See below link for more details:
http://www.phys-astro.sonoma.edu/obs.../eratosthenes/
I realize that belief in the bible and God isn't too popular around this message board, but if you're of that bent this is what the bible has to say about the earth being round:
(NIV) Isaiah 40:22 He sits enthroned above the circle of the earth,
and its people are like grasshoppers.
He stretches out the heavens like a canopy,
and spreads them out like a tent to live in.
Did Columbus know that the earth was round? How bout this nasa site?
http://pwg.gsfc.nasa.gov/stargaze/Lcolumb.htm
So why did my teachers tell me the whole flat earth crap in school? Who knows?
Sorry, didn't mean to be a thread jumper