Installation art is art that is more than three-dimensional—it creates a complete environment. Entire gallery spaces can be devoted to a single installation, usually—but not always—temporarily. Installation art became popular in the 1970s and continues to be an important art form today. Installations rely upon the interactions of the viewer/participant and can even be collected, which means they are not necessarily site-specific. Yves Klein created one of the first installations with his work The Void in 1958. For this work, Klein presented a completely empty, white-walled gallery. Other famous examples of installation art include British sculptor Rachel Whiteread’s Embankment (2005), which she created for the Turbine Hall at the Tate Modern museum in London. The piece consisted of tower-like mountains made of thousands of white, plaster casts of boxes. Visitors to the gallery were able to move through the installation—allowing them to engage with a monumental art form on an intimate level.