The Octagon Earthworks in Newark are 5 to 6 feet tall. There is a 50-acre octagon with sides 550 feet long. It adjoins a circle that covers 20 acres. The mounds appear to have been an ancient astronomical center.

AKRON, Ohio — Ohio is filled with lots of history. There are presidents (eight in all), Indians, a Revolutionary War fort, a War of 1812 naval battle on Lake Erie, the National Road and the Ohio & Erie Canal.

There are figures from Annie Oakley and Gen. George Armstrong Custer to the Wright Brothers and Thomas A. Edison. There are three top Union Civil War generals: Ulysses S. Grant, William T. Sherman and Phillip Sheridan. There is moon walker Neil Armstrong. There are industrial giants like John D. Rockefeller.

But for me, there are two sites in Ohio that offer the best history in the Buckeye state.

They are the mysterious earthworks built by prehistoric American Indians: the Serpent Mound State Memorial near Peebles in Adams County and the Newark Earthworks State Memorial in Newark in Licking County in east-central Ohio.

Honorable mentions go to three other Hopewell sites: Fort Ancient State Memorial in Warren County; Hopewell Culture National Historic Park in Chillicothe; and little-known Fort Hill State Memorial in Highland County. A great source on Ohio’s Hopewell sites is www.ancientohiotrail.org.

But start your visit to Ohio’s past at the Serpent Mound, Ohio’s biggest mystery and what is likely an elaborate astronomical calendar.

The 1,348-foot-long earthwork appears to be in the shape of an undulating snake with seven curves and a spiral-coiled tail. It sits on a bluff 90 feet above Ohio Brush Creek. The site is owned by the Ohio Historical Society and managed by the nonprofit Arc of Appalachia Preserve.

No one knows who built the serpent or why it was constructed, but it obviously was a major religious or mythical symbol to its makers.

The grass-covered mound is 2 to 6 feet high and 20 to 25 feet in width as it stretches and rolls for nearly a quarter mile. The bottom of the mound is yellow clay from nearby pits and rock covered with soil.

It is the largest and most outstanding serpent effigy in the United States (others have been found in Ontario and Scotland) and one of Ohio’s only effigy mounds. It is a National Historic Landmark and on the National Register of Historic Places.

The head of the snake is aligned with the summer solstice sunset and the coils may point to the winter solstice sunrise and the equinox sunrise.

The earthworks may have been built atop where a meteor or asteroid crashed into the Earth. Some rocks rose 1,000 feet and others sank 400 feet for reasons that befuddle geologists. Whatever happened — a meteor, a volcanic eruption — occurred 200 million years ago. It affected 15 square miles around where the Serpent Mound is now.

There is no evidence that the Indians who built the serpent mound buried any dead in it. They were buried in other nearby mounds.

The site was first surveyed by Ephraim Squire and Edwin Davis of Chillicothe, Ohio, in 1846. Harvard University archaeologist Frederic Ward Putnam visited in 1885 and purchased the site to protect it. He spent three years excavating the effigy and nearby conical mounds. He suspected the mounds were built by Adena Indians (800 B.C. to A.D. 100).

More recent radiocarbon testing of charcoal from the Serpent Mound dates it to the Fort Ancient Indians in the 11th century.

Harvard turned the site over to the Ohio Historical Society in 1900. The 54-acre site is off state Route 73 about 10 miles north of Peebles in Bratton Township, about four hours from Akron. Admission is free but there is a $7 parking fee.

There is a small museum, and an observation tower offers an up-high look at the earthworks.

Hours are 10 a.m. to 5 p.m. weekends in April and May, 10 a.m. to 5 p.m. daily June through October, and 10 a.m. to 4 p.m. weekends November through Dec. 18. It is also open for the winter solstice.

For information, call 937-587-2796 or 800-752-2757 or check out www.ohiohistory.org/places/serpent, www.arcofappalachia.org or www.serpentmound.org.

At Newark, you can see remnants of the world-class earthworks built between 100 B.C. and 500 A.D. by the ancient Hopewell Indians between the South Fork of the Licking River and Raccoon Creek.

The mounds and walls once covered more than four square miles and were connected by embankment-lined avenues.

The complex may have been a ceremonial center and an ancient astronomical site to track the moon. It has been described as part temple, part cemetery, part observatory.

The best place to start your visit to the Newark Earthworks State Memorial is at the Octagon Earthworks, the most impressive of three surviving features here.

The Octagon covers 138 acres off North 33rd Street, with mounds 5 to 6 feet high. There are mounds built inside the 50-acre octagon near the openings between the 550-foot-long sides.

An adjoining circle covers an additional 20 acres. The circle is 1,054 feet in diameter and nearly perfectly round.

Researchers have found that the Octagon Earthworks track eight lunar alignments that cover the moon’s 18.6-year cycle.

The Octagon Earthworks were part of the largest system of connected geometric earthworks built anywhere in the world. At one time, there were two circles, a giant oval, a square and an octagon with connecting walls. There were also a number of burial mounds within the complex. The complex required the excavation of an estimated 7 million cubic feet of soil.

Large portions of the walls and many of the mounds have been obliterated by development. Perhaps one-third survive.

The Moundbuilders Country Club is laid out atop part of the Octagon mounds. The club offers limited public access to the earthworks for self-guided tours on Mondays in the winter, on Monday mornings the rest of the year and on four no-golf days.

You can visit the site at other times but you will be restricted to standing on a wooden viewing platform overlooking the golf course.

The two other surviving earthworks in Newark are the Great Circle Earthworks with its small museum and the Wright Earthworks.

The Great Circle is a 66-acre parcel containing a large grassy circle with mounds nearly 1,200 feet in diameter off state Route 79 between Parkview Drive and Cooper Street.

The mounds range from 5 to 14 feet in height and are covered with trees. The inner part of the circle covers 26 acres. There is a small mound at the center. The circle is big enough to hold four football fields laid end to end. It has the feel of a park and a cemetery.

The Wright Earthworks covers two city blocks off Grant Street and features an L-shaped embankment that is 200 feet long. That was once part of a square that was 950 feet on each side and covered 20 acres.

It can be viewed from James Street, a short distance from the intersection of Grant Street and state Route 79.

There is a move to get the Newark Earthworks designated as a UNESCO World Heritage site. The nomination, advanced by the U.S. Department of the Interior, also includes three other Ohio sites: the Chillicothe mounds, the Serpent Mound and Fort Ancient. A decision will not be made until 2013.

The Great Circle and the Wright site are both open daily from dawn to dusk.

Some archaeologists believe that there may have been an ancient roadway that stretched 60 miles from Newark to Chillicothe, where there are more Hopewell mounds.

For more information, contact Newark Earthworks State Memorial at 455 Hebron Road (state Route 79), Heath 43056, 740-345-8224 or 800-589-8224.

The museum is open from 8:30 a.m. to 5 p.m. weekdays, 10 a.m. to 5 p.m. Saturdays and 1 to 5 p.m. Sundays. There are no weekend hours between Labor Day and Memorial Day. The Internet site is www.ohiohistory.org or www.escapetolickingcounty.com.

Newark is 30 miles east of Columbus.