Buried beneath the broken concrete, faded hopscotch squares, and steel slides of the playground at P.S. 261 in Brooklyn may lurk the kind of secret treasures children dream of finding.

Almost an entire city block of elegant brownstones and businesses were bulldozed in the 1950s to make way for the yellow-brick elementary school in Boerum Hill. The Brooklyn Enameled Furniture Manufactory, a milk route storage shed, a Swedish Salvation Army outpost, and the home of a Civil War captain killed in battle were all demolished.

While the buildings are long gone, a local historian, Erik Fortmeyer, who lives in a brownstone overlooking the school, is certain that some buried bootie remains.

“I want to know what the neighborhood was like before the bulldozers came,” Mr. Fortmeyer said yesterday at his real estate office on Atlantic Avenue.

The city has promised to renovate the dilapidated playground that stretches between Pacific and Dean streets, and Mr. Fortmeyer is working out a deal to conduct an archaeological dig when the renovations begin. He believes some treasures can be pulled from the old bathrooms.

In the late 1800s, many Brooklyn families dumped their trash in the “privies,” or outhouses, at the back of their homes. Children tossed glass bottles and marbles into large holes that reached about 12 feet deep. The practice ended when the city started collecting garbage, Mr. Fortmeyer said.

He recently dug out the privy in his own backyard and found a cobalt glass bottle from the William P. Davis soda manufacturer that was located along the Brooklyn waterfront, along with children’s toys and marbles.

About eight privies are likely still intact below the playground, which was never excavated, he said. In total, about 30 brownstones were destroyed to build the school.

Mr. Fortmeyer, a real estate agent and frequent contributor to Antique Bottle and Glass Collector magazine, said the P.S. 261 project has been years in the making. He tracked down old Sanborn Insurance books from an antiquarian in Annapolis, Md., and pored through pages of the old Brooklyn Eagles, a now-defunct daily newspaper.

Last night, he was scheduled to present the project to a meeting of the Boerum Hill Association.

If successful, some of the recovered objects will go on display at the school, where students are beginning to learn about the Civil War. Captain Le Fort, who was killed in battle in 1864 while “gallantly” leading his company, once lived at that site. His body was embalmed and brought to his wife and three children living at 272 Pacific St., according to an announcement in the Brooklyn Eagle.

Some parents at the school said yesterday that they are interested in their children learning about history, but wanted to make sure archaeological forays don’t get in the way of their children’s time outdoors.

“I’m very interested in preserving artifacts,” a parent, Molly Seitz, said. “But you have about 700 children who need a place to play.” Because of insurance issues, students will not be able to participate in any digs, but will be able to watch through a gate. Mr. Fortmeyer plans to videotape the process.