Originally, measurements had a concrete or bodily reference: words such as inch, foot, yard, stone refer to objects or body parts that were used as a standard to quantify distance or weight. To use ones steps as a measurement to establish a route in between two points is a sentimental mapping of sorts, an act that reminds us of the way in which we represent the world in relation to sensorial experience. It is also a standard practice of intuitive planning in urban planning, as well as some kind of neurotic way of acting. In Pacing, the latest title of the LiberArs series, the artist drew invisible figures through public space as a form of imaginary architecture. But since there is no goal in the act itself, this mode of walking by numbers is one of the many ways in which Alÿs conveys the physicality of walking by defining specific simple tasks, which nonetheless have a certain historical resonance and a number of cultural implications. In the aftermath of 9/11, along the desolate streets of downtown Manhattan, his aimless deambulation brought him some consolation, for as he had pointed out in his notes a decade before: As long as Im walking, Im not thinking.