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.’