For his first solo exhibition at Denmark's Louisiana Museum of Modern Art, Danish-Icelandic artist Olafur Eliasson has filled an entire wing with a landscape of stones meant to emulate a riverbed (+ slideshow).
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Described as a "stress-test of Louisiana's physical capacity" the installation by Olafur Eliasson, part of an exhibition titled Riverbed, is a staged imitation of a natural landscape within the walls of one of Denmark's important Modernist buildings.

Bihisti
Acting as a curator in 1999, the artist Pushpamala N organized Sthalapuranagalu, a dialogue with the city of Bangalore, its public spaces, statuary, and ecology.[15] Shamala, one of the featured artists, created a floating installation on Ulsoor Lake (one of several water-bodies in the city, which are slowly drying out due to public encroachments and indiscriminate use of underground water aquifers) from bamboo shafts and wax casts of plastic hearts.

Banks Violette, as yet untitled (TriStar horse), video projection on water vapour
Land Art Installation “Is Our Water Safe in Your Hands?“ at Omaruru River, Artist: Hanne Marott-Alpers (for Land Matters in Art – Namibian Art Project) 
This Land Art Installation consists of 5000 reeds with a blue cloth or plastic wimple attached. The reed wimples are placed in the shape of a spiral in the middle of the Omaruru River, East of the bridge, covering approximately 9240 sqm, 330 meters long and 28 metres wide, giving an impression of the river running. The idea is to create a sensation of surrealism and magnitude to prompt awareness of the fact that all water utilised in Henties Bay and most of Swakopmund comes from the bone dry ephemeral Omaruru River.

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this dry lake bed. The zigzag looks like the pattern reflected light makes on wind blown water. As the stitch recedes into the distance, it breaks apart, like viewing something under water.