Call it the Miami Concentric Circle.

Archaeologists exploring the heart of downtown Miami have unearthed two concentric rings of ancient post holes reminiscent of the Miami Circle that members of the same team discovered directly across the river in 1998.

''We have found another of those missing pieces of Miami history, beautifully preserved under a parking lot,'' said archaeologist Bob Carr of Davie, who also was instrumental in the discovery of the Circle.

The now-famous Miami Circle is 38 feet wide and sits on the south bank of the Miami River. It attracted worldwide interest, stirred considerable controversy and ended up blocking a major development.

The newly discovered circles create a 36-foot-wide feature -- apparently marking the foundation of a prehistoric house -- and were found on the north bank of the river, at the sprawling Metropolitan Miami development site near the InterContinental Hotel.

Builders plan condominiums, stores and offices for the six acres. Scientists say the discovery should not interfere with development, but it is scientifically and culturally significant.

Though major differences exist between the Miami Circle and the concentric circles, Carr said they both are about 2,000 years old and share the same creators -- the Tequesta tribe, South Florida's original occupants.

The Tequesta lived on both sides of the river for as long as 2,500 years.

By 1763, they were gone, rendered extinct by European explorers and the diseases they carried.

''Now, we have another physical, material record of people who were here before us -- that continuity, that sense of place that is really important,'' Carr said as his team dug out and marked new discoveries Tuesday, including the jaw bone of a dog found buried just outside the concentric circles.

He noted that the new circles are close to the original shoreline -- ''prime real estate,'' he called it -- and apparently helped form one of many ancient house foundations that could be unearthed as the exploration continues.

'FOOTPRINT' OF HOME
''We believe this is the footprint of a Tequesta home, something that gives us a lot of clues about the way the Tequesta lived,'' he said.

The purpose of the double ring of circles is unclear: The house might have had two sets of posts, Carr said, or a larger house might have replaced the original one.

In any event, archaeologists believe that gaps in the pattern of holes show a doorway on the northern edge and possibly on the southern edge of the formation.

Carr, who worked for Miami-Dade County when his team discovered the Miami Circle, now runs the Archaeological and Historical Conservancy.

The nonprofit group was hired by the Metropolitan Miami developer to perform a legally required archaeological assessment of the site.

More elaborate and substantial than the concentric circles, the Miami Circle is comprised of 26 carved basins and apparently had ceremonial and possibly commercial purposes over the centuries, making it far more worthy of preservation, Carr said.

The concentric circles are quite different, he said.

''These are much more subtle holes,'' Carr said. ``They are much smaller, just large enough to support posts.''

The team found beads and crushed animal shells in some of the holes. Elsewhere on the development site, it found some scattered human bones and thousands of beads, pottery shards and other artifacts.

The developer, MDM Development Group, previously promised to display cultural artifacts in one of the plazas planned for the project. On Tuesday, the company also pledged to preserve the concentric circles -- either in a plaza, a museum or both.

''This will have no effect whatsoever on development,'' said Gaby Garcia, an MDM spokeswoman.

``It's just post holes and they happen to be in a circular formation.''

Ryan Wheeler, chief of the state's Bureau of Archaeological Research, said he saw the concentric circles and wanted to learn more about what else was found there, but he tended to agree that the discovery would not affect development.

''It certainly seems like it has some similarities to the Miami Circle,'' Wheeler said, ``but maybe it will have a different trajectory.''

Among other things, he and Carr said, the discovery should end any doubt about the authenticity of the Miami Circle.

Some critics have suggested that the Circle was formed by phenomena like rain or runoff from a nearby sewage pipe.

BUILDING TEMPLATE
''It looks like the Tequesta had a unit size for their buildings, a template that they used,'' Carr said, ``just like some of our builders today use a blueprint for ranch homes.

``Scientifically, this really cements the validity of the Miami Circle.''