The Vertical Earth Kilometer, located in the Friedrichsplatz Park in Kassel, Germany, is a one-kilometer long brass rod five centimeters (two inches) in diameter. The full length of the rod is inserted into the ground with the top lying flush to the surface of the earth. A red sandstone square surrounds the brass rod’s flat circular top, commemorating the undistinguished top of the pole, which could otherwise be mistaken for a large blank coin.

Installed in 1977, the VEK is the work of famed American artist Walter De Maria, whose other work with metal rods includes the Lightning Field and the Broken Kilometer. But this is by far De Maria’s most subtle, and bizarre, work. The piece is almost entirely hidden from view, confining its existence to the trusting mind of the viewer. The boring of the shaft, which goes through six geological layers, took seventy-nine days. The continuous metal rod is made up of lengths measuring 167 meters each, that are screwed tightly together. The sandstone square which surrounds the top of the shaft is at the intersection of two paths which traverse the Friedrichsplatz in Kassel, Germany, site of the international contemporary art survey, Documenta.