The Effigy Tumuli earthwork consists of five geometrically abstracted animal forms, created on old mining land along the Illinois River. Now a state park, the sculpture is in flux, parts eroding, parts overgrown, others nearly bare. It is one of the largest artworks in the country, and the shapes are so large that they can only be discerned from the air. On the ground, one experiences mounded earth, paths, interpretive signs, drainage control gullies, and patches of grass, shrubbery and exposed earth. Michael Heizer was commissioned to make the sculpture in 1983, by the president of the Ottawa Silica Company, who had an interest in art and whose company owned the site. The property had been strip-mined for coal, and was a polluted and eroded barren landscape, with highly acidic soil. For this "reclamation art" project, instead of drawing on his vocabulary of abstract forms, Heizer used figurative forms, creating mounds shaped like animals native to the region. There is a snake, catfish, turtle, frog, and a water strider (the legs of which can be seen in the photograph above). He considered these figures to be evocative of the Indian mounds that can be found throughout the Midwest, and intended his sculpture to be a statement for the Native Americans. A trail wanders through the 1.5 mile long site, with remnants of interpretive signs that once depicted maps of the site to help to give visitors a sense of what they might be looking at, but are now mostly blank. Heizer seemed pleased that the forms were imperceptible from the ground, saying the piece "requires a chronological development of perception."