This is a day in which all art galleries from the Miguel Bombarda Cultural Circuit (which comprises the following streets: Rua Miguel Bombarda, Rua do Rosário, Rua do Breyner, Rua D. Manuel II and Rua Adolfo Casais Monteiro) simultaneously present new exhibitions and new collections.

Also, there are shows on the street and performances, among other things.

Image taken from here.