During the Olympics, Anthony McCall’s ‘Column’, a sort of anorexic tornado, will punctuate Liverpool’s skyline. Pipes rotate and heat the water of the River Mersey, creating the spinning, sinuous cloud. It may only be an 80 ft.-wide thread of mist twirling 1.2 miles into the sky, but this $780,000 Olympic commission has already caused controversy. In April the Civil Aviation Authority pointed out that ‘Column’ was on the flight path to John Lennon Airport, and insisted on tests to see if it would affect airplanes. So far, the twister has yet to wind its way into Britain’s skies.