Picture Post: Top dog - Koons up on the roof

On Monday evening in New York, Jeff Koons found what seems the perfect place to symbolise his primacy over the American art market: the roof of the Metropolitan Museum of Art. Over his career, the Manhattan artist has exhibited vacuum cleaners and floating basketballs as works of art.

He has beguiled and teased gallery visitors with giant teddies, stainless steel bunnies and a 43-feet-high statue of a West Highland terrier. He has generously offered us paintings and glass sculptures displaying himself and his then-wife Ilona engaged in strenuous sexual congress in a sylvan bower (thanks, Jeff). Last November, at Sotheby's New York, his pink steel Hanging Heart – a giant version of the cheap pendants they used to give away free with teen magazines – went for a heart-stopping £11.3m.

The Cantor Roof Garden at the Met mounts a seasonal outdoor sculpture show every spring. This year it is Koons's turn, and he is showing off three sculptures in the idiom with which he's most at home: a blown-up, buffed-up, glossily shiny version of small objects. In this case, a chocolate heart wrapped in red cellophane, a twisty-balloon dog, and a badly coloured picture of Piglet from a Winnie the Pooh colouring-book.

The New York Times critic was enraptured by the "intellectually and sensuously exciting" sculptures, calling the balloon dog "a sly Trojan Horse: it seems innocent but is loaded with aesthetic and erotic perversity". The same writer, however, did question the value of exhibiting the pieces on the gallery roof, where they're dwarfed by the sky. Their whole point as artworks, after all, is to disconcert the indoor viewer by their inappropriate hugeness. Someone failed to think this through.

Koons will not care, though. Some day he should exhibit a sculpture showing his bank balance, blown up to dismayingly enormous proportions.

Jeff Koons on the Roof is at the Metropolitan Museum of Art, New York until 26 October