I t doesn't sound like the kind of thing you'd take your children to see: a 3.5-meter-high, gleaming marble statue of a naked woman who is not only eight-plus months pregnant but also physically deformed, with no arms and stunted legs. Yet just such a statue was installed in London's refurbished Trafalgar Square last month, and it has sparked quite a fruitful debate about public art vs. "museum art" -- about art in general, really.

Trafalgar Square has not historically been known as a go-to place for art, at least not the outdoor kind. (The National Gallery, on its north side, has fine examples of the indoor kind.) There are plenty of statues, but with the exception of a small sculpture of Minerva, they are all standard products of the heroic school: men (either kings or soldiers), horses and lions. Towering over the lot of them atop a 52-meter column is Lord Nelson, the one-armed, one-eyed hero of Trafalgar. Around the square sit four great pedestals, or plinths. The most interesting thing about these is that only three are occupied. The fourth plinth, in the northwest corner, was supposed to hold another man on a horse, but funds ran out and it has stood empty for most of its 164 years.

Which is where the fun began. A few years ago, as London's mayor drew up plans to turn the stately but stodgy square into a lively piazza, a government-appointed committee recommended using the fourth plinth for a permanent rotating display of modern pieces. The first selection, Marc Quinn's head-turning "Alison Lapper Pregnant" depicts a brand-new kind of hero -- a female artist friend of his with congenital deformities. And although it has been in place only a month, the buzz has yet to die down.