The casual visitor to this small rural community about 15 miles west of Lake Okeechobee might barely notice the broad indentations that run for seven miles from a cluster of oak-shaded mounds through scrub pine and palmetto to the Caloosahatchee River.
But to archaeologists they are monuments to prodigious engineering skill and hard work -- canals that enabled Indians to travel between Lake Okeechobee and the Gulf of Mexico.
Around A.D. 250, Indians inhabiting this area began digging the canals by hand, using wooden and shell tools to create waterways 20 feet wide and 3 to 4 feet deep, said Robert Carr, the Florida archaeologist who directs excavations at the site.
Their goal was not to drain or irrigate land, Mr. Carr said, but to create a waterway to bring dugout canoes to their village, a mile north of the Caloosahatchee. The canals also allowed paddlers to bypass rapids roiling the river.
The two-square-mile village at the center of this watery network was a planner's dream, with sculptured earthworks (one of them resembling a crescent moon holding a star) and mounds, ponds and geometric causeways. Eventually, the people, known today as the Ortona, added a 450-foot-long pond, shaped like a ceremonial baton and surrounded by a beach they made with white sand.
''In adapting to their wetland world, the people of South Florida achieved a level of cultural sophistication and social organization much earlier than previously believed,'' said Mr. Carr, executive director of Archaeological and Historical Conservancy in Davie, Fla.
And the dates place the Ortona people squarely within an American Indian tradition, that of the Hopewell people, whose center was far to the north, in the Ohio River Valley. Archaeologists have long theorized such a connection, primarily because of the design of mounds and artifacts. But they lacked hard evidence.
''Now, with these dates, Bob Carr has provided the smoking gun for placing peninsular Florida within the Hopewell culture,'' said Dr. James A. Brown, a professor of anthropology at Northwestern University, who was not involved in Mr. Carr's excavations.
Humans apparently occupied Ortona around 700 B.C. and lived there at least 1,500 years, Mr. Carr said. But the Ortona people's greatest cultural achievements occurred from A.D. 200 to 700, radiocarbon dates from recent excavations indicate. Similar bursts of construction appeared about the same time in other parts of South Florida. On one site, at the mouth of the Miami River, Indians carved a circle 38 feet in diameter into limestone, said Mr. Carr, co-discoverer of that site in 1998.
With a population of 200 to 300, the Ortona village was a major center for the exchange of goods and religious and cultural ideas from other parts of the country, Mr. Carr said.
In their dugout canoes, traders plied the rivers flowing to and from Lake Okeechobee like spokes on a wheel. They also paddled up and down the Gulf and Atlantic Coasts of Florida, and even beyond.
Archaeologists have long reasoned that a major trade route ran from Lake Okeechobee down the Caloosahatchee to the Gulf of Mexico and up the Gulf Coast to the Apalachicola River in the Florida Panhandle. From there it followed the Chatahoochee River north and ultimately crossed the Allegheny Mountains at Cumberland Gap to reach the Ohio River Valley.
Alligator and shark teeth and skins, feathers from Everglades birds and shells were carried north, Dr. Brown said; flint, copper, beads and possibly effigy pipes moved south. And travelers carried a host of ideas about the cosmos, marriage and burial rituals and shamanistic rites.
These ideas and many of the goods were related to the Hopewell culture, which originated in the Ohio Valley around 100 B.C. At its height, from A.D. 200 to 400, the Hopewell people built mounds, enclosures and causeways in the Midwest and much of the Mississippi River Valley, and even more extensive trade routes, Dr. Brown said.
But in a significant departure from the Hopewell tradition, Mr. Carr said, the Ortona people and their neighbors in South Florida built mounds for their homes, as well as for burials and ceremonies. ''Placing structures on mounds was a special South Florida adaptation to the wet environment,'' he added.
The Indians of South Florida traveled chiefly by dugout canoe, going deep into reaches of the Everglades that many white settlers later considered impenetrable. It is not surprising, then, Mr. Carr said, that the Ortona people built canals to speed their travel. ''The Ortona canals are the earliest we have found devoted to transportation,'' he said.
The Ortona canals formed a triangle, with the Caloosahatchee River as the base and the village as the apex. A western canal ran about four miles; an eastern canal, about three.
Mr. Carr's team established the age of the canals with carbon 14 dating. The researchers -- Mr. Carr, Jorge Zamanillo of the Historical Museum of Southern Florida and Jim Pepe of Janus Research -- published their report in the March issue of Florida Anthropologist.
The Ortona canals appear to be part of a more extensive network of canals and dugout canoe trails that crisscrossed the Everglades and ran along the coasts, said Dr. Ryan J. Wheeler, senior archaeologist with Panamerican Consultants, who has studied the waterways.
Little is known about the Ortona people, but Mr. Carr speculated that they might have built some or all of the 20 other groups of mounds and circles around Lake Okeechobee. He added that they were probably ancestors of the powerful Calusa, who occupied southwest Florida and controlled tribes around Lake Okeechobee, and the Mayami, who lived south of the big lake. Those tribes flourished from around 1200 until Spanish settlement in the early 16th century.
By the time Spain ceded Florida to England in 1763, virtually all of Florida's indigenous people had vanished, victims of warfare and disease, particularly smallpox. Their cultures and histories were lost with them. When American surveyors discovered the Ortona earthworks in the early 19th century, they thought they were Spanish fortifications, Mr. Carr said.
Seminole and Miccosukee Indians were driven into the Everglades region during the Seminole Wars of the 19th century.
The landscape and earthworks of the earlier Floridians have changed drastically as well. Hamilton Disston, a toolmaker from Philadelphia, destroyed the rapids of the Caloosahatchee River in the early 1880's, during the first concentrated effort to drain the Everglades.
A century of drainage and development have further altered the environment and carved up the Ortona earthworks. The vegetation-covered dry indentations that were the canals, best seen now from the air, lie mostly on private land, their preservation dependent on the owners.
The Baton Pond, built before 700, according to a recent, unpublished analysis, is also mostly obscured, although the owners of the site are working with Mr. Carr to preserve it.
Some of the 25 Ortona earthworks are protected in Ortona State Park, but others, including a 60-foot causeway, are unprotected. Sand mining and development have taken a toll on many, including a 20-foot-high burial mound -- the highest point in Glades County. The burial mound was largely destroyed by road building in the 1940's and 50's, Mr. Carr said.
Over the years countless Florida archaeological sites have suffered the same fate, usually before anyone could investigate them, he added.
''The prehistoric settlement pattern across South Florida is still largely unknown,'' Mr. Carr said. ''Lake Okeechobee was the hub, and it is one of the least protected areas in the state. We have to help preserve what's left, or it will be gone in the next 20 years.''