He suspects it is a symbol meant to conjure up the notion of the unity of opposites, like the yin and yang, or a geometric representation of Christ as the philosopher stone. And he believes it is the work of the celebrated American architect Ithiel Town. Town's New York City handiwork includes Federal Hall, where, Solomon notes, similar pyramidal shapes can be found on the marble floor. But the more telling clues, he said, are the geometric exercises painted in the background of a portrait of the architect that hangs in a church in New Haven, Conn.

"This same geometry has turned up in his documents," Solomon said of Town. "He seemed to have a taste for this sort of stuff."

The brickwork-a 10-foot-tall stack of three triangles, the center one being the largest-was uncovered at 211 Pearl St. in 2001 as the building's interior was demolished to make way for a parking garage. The triangles were built into the wall when the Greek Revivalist-style building was constructed in 1832. Solomon, an amateur historical slueth, was hired to research the building's history in a failed effort to save it from the wrecking ball. Now what is left is the building's facade and that symbol on an interior wall, which Solomon believes is significant and should be preserved.

But there is no proof that Town was the building's architect. Nor is there proof that William Colgate, the soap magnate who commissioned the building as a counting house in 1832, ever saw the symbol. It was covered with wall plaster.

Located just 10 feet from the mouth of the garage, it would be visible from the street if not for the sheet of plywood mounted over the top. Solomon fears that the plywood only serves to hide the symbol until the developer, Rockrose, has it removed altogether. Rockrose did not return messages left by the Trib.

In December Solomon took his concerns to the Landmark's Committee of Community Board 1. The lights in the meeting room were dimmed and committee members leaned into the conference table for a closer look at the mysterious image glowing on Solomon's laptop computer.

"We could use a good séance," joked City Councilman Alan Gerson, who walked in during the presentation to find the community board members huddled in the dark.

"It's an odd sort of thing," Gerson said following the presentation, but he joined the board in a promise of support for the symbol's preservation.

The state's office of Parks, Recreation and Historic Preservation wrote to Solomon in September, saying that his research into the symbol would be included in their files.

But to be saved, the symbol needs the protection of the city's Landmarks Preservation Commission, which requires proof that the symbol is historically or culturally significant. A spokeswoman for the commission said last month that Solomon's research was still being evaluated and that no decision had been made about whether the symbol merits landmark status.

Roger Byrom, chairman of CB1's Landmarks Committee, said the board would appeal directly to the developer to preserve the symbol.