Observations: Antony Gormley's New York's statues set to be a towering success

With so much to occupy the senses at ground level in New York City, it's all too easy not to look up. But cast your eyes above the crowded pavements and mirrored office windows surrounding Madison Square Park and you soon begin to spot them.

One on the roof of the beautiful Flatiron Building. Another on the mighty clock tower at the bottom of Madison Avenue. A third above an unassuming office block on East 26th Street. The longer these shadowy figures stand guard, the harder it is to tell whether they're there to watch or be watched.

'Event Horizon', Antony Gormley's installation of 31 life-size fibreglass and cast iron statues that first peopled London's South Bank in 2007, has finally transferred to midtown Manhattan. Remarkably, it's the artist's first public exhibit in New York and, like many of his projects, it's already sparking controversy.

In London, police were inundated with calls from onlookers worried they were witnessing a suicide attempt. The NYPD are reporting the same, but concern here runs deeper. "You can't help but think of those people jumping off the Twin Towers," says one troubled passer-by. "It's too soon for an exhibition like this." However, those in line at Shake Shack, New York's trendiest burger outlet, are already playing spot-the-statue while they wait for their fries.

That Gormley was green lit at all is partly thanks to fellow Brit Sean Kelly, a heavyweight of the New York gallery scene who has known the artist since the early Eighties. "This is the best view," says Kelly, dragging me out in front of an army of yellow taxis on Fifth Avenue to point out statues as far at 14th Street to the south and the Empire State Building to the north. "They say New York is a vertical city, but nothing has highlighted it quite like this before." And Kelly's right. It's traffic-stopping stuff, which, in this city, is no mean feat.