For a description of the festival we have this excerpt of a conversation between Socrates and a friend describing that festival (from Plato's Republic):
"Sokrates: "I went down yesterday to the Peiraios (Piraeus) with Glaukon (Glaucon), the son of Ariston, to pay my devotions to the Goddess [Bendis], and also because I wished to see how they would conduct the festival since this was its inauguration. I thought the procession of the citizens very fine, but it was no better than the show, made by the marching of the Thrakian contingent [i.e. the mercenary force who policed ancient Athens]. After we had said our prayers and seen the spectacle we were starting for town... "
"'Do you mean to say,' interposed Adeimantus, 'that you haven't heard that there is to be a torchlight race this evening on horseback in honor of the Goddess?' "
"'On horseback?' said I. 'That is a new idea. Will they carry torches and pass them along to one another as they race with the horses, or how do you mean?' "
"'That's the way of it,' said Polemarkhos, 'and, besides, there is to be a night festival which will be worth seeing. For after dinner we will get up and go out and see the sights and meet a lot of the lads there and have good talk... Let this complete your entertainment, Sokrates, at the festival of Bendis.' "