It took the Metropolitan Museum of Art nearly 50 years to wake up to Pablo Picasso. It didn't own one of his paintings until 1946, when Gertrude Stein bequeathed that indomitable quasi-Cubistic picture of herself - a portrait of the writer as a sumo Buddha - to the Met, principally because she disliked the Museum of Modern Art.

All of Koons's best art - the encased vacuum cleaners, the stainless-steel Rabbit (the late-twentieth century's signature work of Simulationist sculpture), the amazing gleaming Balloon Dog, and the cast-iron re-creation of a Civil War mortar exhibited last month at the Armory - has simultaneously flaunted extreme realism, idealism, and fantasy.

Venice is the perfect place for a phase of art to die. No other city on earth embraces entropy quite like this magical floating mall.

Appropriation is the idea that ate the art world. Go to any Chelsea gallery or international biennial and you'll find it. It's there in paintings of photographs, photographs of advertising, sculpture with ready-made objects, videos using already-existing film.

After its hothouse incubation in the seventies, appropriation breathed important new life into art. This life flowered spectacularly over the decades - even if it's now close to aesthetic kudzu.