Taken in the Turbine Hall, Tate Modern London. Blurb from http://www.tate.org.uk :
In this installation, The Weather Project, representations of the sun and sky dominate the expanse of the Turbine Hall. A fine mist permeates the space, as if creeping in from the environment outside. Throughout the day, the mist accumulates into faint, cloud-like formations, before dissipating across the space.