Water hyacinth grows into a thick bed of waxy leaves and violet flowers that cover the surface of the lake.

CNN: Flower power threatens Kenya's Lake Victoria

In an effort to mimic the soft exterior of a real bed, Mr. Fischer coated one of the bed sculptures with white paint but then interrupted the smooth surface by pouring a pile of real concrete over it, weighing down one side of the sculpture's surface.

WSJ: Urs Fischer's Beds & Problem Paintings Show in Beverly Hills

There are river channels and flood plains galore on the planet's surface, and even a hemisphere-wide depression that many interpret as an ocean bed.

ECONOMIST: A drought on Mars