in 52BC, after a long siege, Julius Caesar and his army finnaly won the battle of Alesia against a confederation of Gallic tribes united under the leadership of Vercingetorix.
The siege of Alesia is considered one of Caesar's greatest military achievements and is still one of the classic examples of siege warfare and circumvallation.
The refusal of the Roman senate to allow Caesar the honour of a triumph for his victory in the Gallic Wars eventually led, in part, to the Roman civil war of 50-45 BC.
see : http://en.wikipedia.org/wiki/Battle_of_Alesia
but since those days nobody knows exactly where is the exact location of Alesia. Many theories has been suggested.
Alise-Sainte-Reine in Burgundy is the "officiel" location but many others searchers think that Alesia is somewhere else. At least 30 places has been suggested (http://www.alesia.asso.fr/pg/Alesia/Polemique/alesia-polem-icietla.htm)
I give here the placemarks of 8 locations among the most famous.