Kimsooja’s Room of Rainbows in Crystal Palace Buen Retiro Park, Madrid Spain. Created in 2006 by multidisciplinary artist Kimsooja, To Breathe – A Mirror Woman was an elaborate installation at the Palacio de Cristal, Parque del Retiro, in Madrid. 

Originally built in the late 1880s to house a collection of flora and fauna from the Philippines, Kimsooja transformed the Palacio de Cristal into a multisensory sound and light experience. A special translucent diffraction film was used to cover the windows to create an array of naturally occurring rainbows which were in turn reflected by a mirrored surface that covered the entire floor. (Source)