The site was investigated by BBC2 documentary A History of Ancient Britain, with presenter Neil Oliver describing it as "the discovery of a lifetime".
It was most likely used for rituals and ceremonies during the Neolithic Age.
Skara Brae is a domestic settlement close to the Ness of Brodgar.
It is Europe's most complete Neolithic village and was first uncovered in 1850 when a storm struck the islands.
Both sites have revealed some fine Neolithic art, with a key piece of carved stone found at Ness Of Brodgar in August last year.