Florence is one of the two or three cities that sit on top of the art world. It has most of Michelangelo's greatest sculptures, all of Botticelli's greatest paintings, Bernini's greatest bust, and the two best Italian-Gothic churches. It has the lions' share of the world's great 13th, 14th and 15th century paintings, as well as the lion's share of the paintings and frescoes (by Paolo Ucello and Massacio) that invented "perspective." It has the prettiest cathedral in Italy, with the best dome in Europe. It is not a city you go to to see modern art.

So I was surprised during a recent visit to walk by the Palazzo Strozzi—the Medici-rival Strozzi-family's castle-esque home, now a museum—and see signs advertising a show called "From Kandinsky to Pollock." I went inside for a look.

It was a show of '30s, '40s, '50s and '60s abstract art from the Guggenheim collection: seven superb Pollacks, including some very fine pre-drip paintings; two exceptional De Koonings; two remarkable Hans Hofmanns; two very good Joseph Cornell "boxes"— deep-picture-frame sculptures; a room of Calder mobiles and another of fine Mark Rothkos; plus various assorted pretty-good Kandiskys, Duchamps, Debuffets and Picassos.

It was an exceptional show; the Guggenheim has an exceptional collection. The problem is, it's never on display. The Frank Lloyd Wright spiral-rotunda always (or almost always) hosts a temporary exhibit. Some of the peripheral rooms hold smatterings of the stuff the Guggenheim has in its vaults. If you're lucky, two or three paintings in that smattering, on any given day, will be Chagalls or De Koonings or comparable master-painter's masterpieces. The rest will be unknown works of second- and third-rate artists.

This generation of museum curators, by and large, seem determined to be iconoclastic and unpredictable, to try to show off their frustrated artists' souls. Thanks to them, if you want to see the best modern art in New York, you have to go to Italy.

Joshua Gelernter is a writer in Connecticut.