The mayor listened closely to the artist speak on the Mammy Sphinx, in a moment suspended on a summer afternoon by the Brooklyn waterfront. I'll keep it for a long time.

"The space pulled you," Mayor Bill de Blasio, clad in an olive shirt and khaki shorts, said. He, his wife and artist Kara Walker spoke with the woman who commissioned the public art project, Anne Pasternak, who heads Creative Time. De Blasio's visit came as a surprise, with no speech or fuss, which people found refreshing.

There we stood in the old Domino Sugar factory. Within the walls, the air still smelled tantalizingly of molasses, even with machinery gone. My friend Victoria and I milled around the huge space after standing "on line" with hundreds — my only chance to see the show. I had to hop a train to see this, she told me: How often do you see a Mammy Sphinx of sugar? Make that roughly 80 tons of Domino sugar, several stories high. A lot like the Great Sphinx, a massive block of stone towering near the Egyptian pyramids.

The resemblance hits hard where you live. The female Sphinx figure is nude but for a head kerchief, her familiar face evoking the sad story of sugar in the slave trade. In ancient Egypt, the pharaonic pyramids around the sands were built by slaves. And the building housing this sphinx was built in 1856, during the American slavery era.

This comforting yet jarring Mammy, our Mammy, is a fleeting sculpture (of styrofoam and sugar) in a free installation that closes July 7, forever. The industrial building will be demolished for posh condos. The short-lived nature heightens the intensity.

"She's bigger than all of us," I heard Victoria say. The Mammy is monumental.

Staring at us: a sweet historical vindication for African-American women enslaved in houses and fields, by day and by night. Sweet vindication is hard to come by, yet this homage succeeds in an almost wordless way. The water's edge echoed the way enslaved West Africans arrived on our shores, in chains on ships that crossed the Middle Passage. That suffering can never be erased, but it can be honored out in the open.

Walker named her work, "A Subtlety, or The Marvelous Sugar Baby." Ironically, her installation is anything but subtle. But the experience takes you through a seamless scene at once ancient, powerfully present — and ephemeral.

Freighted with meaning and memory, the female form confronts visitors with a dual identity. Up front is her face as a caregiver and part of the "family," so close that she breastfeeds babies. Seen from the back is the secret role, her body presented as property to be taken at the master's will, by force.

Just as we were about to go, in walked the artist, the mayor, his wife and Pasternak. So we stayed a while. Williamsburg, Brooklyn was where the city's vibe was, clearly, and we were in no hurry.

Placed here and there are sugary figures of beguiling boys, whose sweetness has not been stolen by slavery. Carrying baskets of molasses melting and streaked with liquid, they suggest the brutal toil and blood that went with cutting cane under the sun.

Before the Civil War broke out, Quakers and other abolitionists shunned sugar.

Simplest fact of all: raw sugar is brown. Sugar is "refined" when bleached white. As the weeks went by, Walker's Mammy became less white. Signs of reclaiming, maybe, or owning oneself.

I heard Pasternak say to the mayor, who cuts a towering figure at 6 foot 5 inches: "It's almost unheard of for a woman artist to make a sculpture this size."

It's also rare to see a politician listen in an arena he could have dominated. De Blasio insisted some of new waterfront housing be set aside as affordable, but the Mammy Sphinx was the reason he came. With him was his wife Chirlane McCray, an advisor and a writer who has worked in politics. He is white and she is African-American.

The arresting show's short time is as apt as the space, simultaneously as we celebrate American liberty and independence on July 4th.

History rolls along, in waves, fits and starts. Sugarcoated as it is.

To find out more about Jamie Stiehm, and read features by other Creators writers and cartoonists, visit www.creators.com.