Richard Serra tilted arc ocated at Federal Plaza in New York City caused much attention just after the sculpture installed.Tilted Arc is a curving wall of raw steel, 120 feet long and 12 feet high, that carves the space of the Federal Plaza in half. Those working in surrounding buildings must circumvent its enormous bulk as they go through the plaza. According to Serra, this is the point, “The viewer becomes aware of himself and of his movement through the plaza. As he moves, the sculpture changes. Contraction and expansion of the sculpture result from the viewer’s movement. Step by step the perception not only of the sculpture but of the entire environment changes.”

(source PBS)