A memorial of granite, stone and water was dedicated Friday at a burial ground where hundreds of slaves and other blacks were interred two centuries ago then forgotten as lower Manhattan expanded above their remains.

The ceremony featuring the singing of spirituals and a spoken word piece by actor Avery Brooks came more than 16 years after the African Burial Ground was rediscovered.

"The tragedy was that for so many years, for centuries, people passing by this site did not know about the sacrifices they had made," said Rodney Leon, designer of the memorial. "Now we have an opportunity to right some of the wrongs of the past."

The entryway to the memorial is called "The Door of Return" — in contrast with the door of no return, the name once given to the departure points where slaves were shipped from Africa to North America.

Alongside the 20-foot-high chamber of gray stone sits a circular court, with a map inscribed into the center. The space has seven grassy mounds marking where some of the disinterred bones were reburied four years ago.

Visitors were permitted inside the space after the dedication. Those in attendance included Mayor Michael Bloomberg and Sen. Charles Schumer, D-N.Y.

The project, from recovery of the bones to reinterment to construction, cost more than $50 million. A museum also is planned.

Until the burial ground was closed at the turn of the 19th century, it was the final resting place for tens of thousands of people of African descent. New York City's vast development since then left the cemetery more than 20 feet underground.

It was rediscovered — along with more than 400 sets of remains — during excavations for a federal building in 1991. The burial ground, most of which still lies deep beneath sidewalks, buildings and streets, was designated a national historic landmark in 1993.

Last year, the site was declared a national monument.