As an unannounced intervention during the 2nd Johannesburg Biennale in 1997, Olafur Eliasson organised the emptying of a water reservoir located opposite the exhibition hall in which one of his photo series was on show. The water turned into a stream, running approximately 1.5 km through the city, carrying dirt, leaves, and litter with it, before disappearing into a sewer. People in the city were forced to navigate the change to their urban environment, which lasted for about three hours. The intervention was again carried out in Oslo in 1998.