On a recent afternoon a team of gravediggers chucked the final shovelfuls of dirt out of a grave dug into a hilltop at Green-Wood Cemetery. The team then winched a marble gravestone weighing 500 pounds up the hillside, preparing an unusual grave. There will be no funeral, no mourners — in fact, no body will be inside the plot.

Dug deep into a hill in Brooklyn will be a grave of secrets.

“Here lie the secrets of the visitors of Green-Wood Cemetery” is etched into the cream marble of the obelisk marking the grave. At its base is a thin slot — a letter opening where slips of paper bearing secrets are to be slid into an underground chamber and taken, quite literally, to the grave.

The grave is the work of Sophie Calle, a French conceptual artist, and was commissioned by Creative Time and co-presented with the cemetery. Creative Time is a public arts organization known for putting on less furtive works, like Duke Riley’s “Fly by Night,” last year, in which pigeons outfitted with LED lights took to the night sky over the Brooklyn Navy Yard like flocks of stars, and a recent, politicized haunted house called “Doomocracy” at the Brooklyn Army Terminal.