The vertical earth kilometre

With the "Vertical Earth Kilometer", the American artist Walter De Maria created a key work of land art and conceptual art in 1977. It consists of a vertical borehole 1,000 meters deep, into which 167 brass rods screwed together are sunk. The work is largely hidden from view: all that is visible is the five-centimeter-wide circular area of the rod diameter in the middle of a sandstone base plate. The invisible work is intended to encourage people to think about the earth and its place in the universe.