When You Go ... Newark Earthworks Day, on Oct. 22, features a variety of seminars and entertainment. Here is a sampling of the scheduled events: 10:30 a.m.-3 p.m: Presentations on contemporary Native Americans and contemporary issues link the past to the present. 3:30 p.m.-6 p.m: Ray Hively, Robert Horn, Bradley Lepper and Tom Burns discuss lunar alignment. 6:30 p.m.: Contemporary Native American Dance by Rosalie Jones ("Day Star"). 7 p.m.: Buses begin transport to the Octagon Earthworks 10:14 p.m.: Moonrise over the octagon Visitors must park on the Newark campus of The Ohio State University, located just north of St. Rte. 16. Parking is available anywhere on campus and events and buses to the moonrise will be at the Reese Center, 1209 University Dr., Newark. For more information, call 740/364-9574 or visit www.octagonmoonrise.org .

It's not every day that you get the opportunity to witness a lunar phenomenon. In fact, it's only once every 18.6 years - and the next time is October 22 in Newark. That evening, the moon will rise at its northernmost point on the horizon, in precise alignment with a series of massive ancient earthworks that were built for reasons still not fully known. As the sunlight begins to wane on this special day in central Ohio, the centuries seem to melt away, too. Here is where an ancient civilization devised what was once the largest complex of geometric earthworks ever built - one of them, a 50-acre octagonal structure, is large enough to hold four Roman coliseums - and constructed them in a manner that, on this night, places their mysterious reverence of the moon on full view.

But, "To call this an observatory is ... too simplistic," says Bradley Lepper, curator of archaeology for the Ohio Historical Society in Columbus, referring to the Octagonal Earthworks, one component of the Newark Earthworks.

Nearly 2,000 years ago, when the latest technology consisted of little more than sticks and baskets, the native people of Ohio sculpted millions of cubic feet of land into giant shapes spread over five square miles in what is now Licking County. An enormous octagon, two circles, an oval - mammoth remnants of the geometric configurations, believed to have been used for different types of ceremonies, still dot the landscape today. They stand as an example of what Lepper calls the culture's "masterpiece - their grandest expression of this whole kind of architecture."

Although these reminders of the civilization remain, a climb up the grassy hillside of the 15-foot observatory reveals that the landscape's view has clearly changed with the times. Today, the vista that was once composed of plains is punctuated by the manicured greens and thick trees of the Mound Builders Country Club. But while it's difficult to imagine the setting exactly as it once was, one thing has remained constant throughout the ages: Every significant rising and setting point in the lunar cycle is encoded in the walls of the giant octagonal earthwork, showing the culture's interest in astronomical events.

"I think the moon was something sacred [to them]," says Lepper. "By incorporating the lines of the moonrise and moonset into the structures, I think it was a way of bringing that magic of the sky world down to earth, and the rituals and ceremonies that took place here were probably intimately related to that."

It wasn't until the early 1980s that astronomer Ray Hively and philosopher Robert Horn of Indiana's Earlham College unlocked some of the secrets of the octagonal earthworks, uncovering their connection to the moon's cycle of rising and setting. Ancient peoples of the region observed that the point on the eastern horizon where the moon appears to rise moves every month until it reaches a maximum (it never rises any farther north than this particular point) and takes nearly 20 years to return there again. Hively and Horn realized that, without so much as a pair of binoculars, a civilization learned this cycle and constructed the octagon earthworks to align with it.

While the seven other significant rising and setting points of the moon are also encoded in the octagon's walls, the architecture of the earthworks specifically frames the unique moonrise that takes place later this month. Ancient Ohioans could stand on the observatory mound, look through the parallel earthen walls that connect the circular and octagonal earthworks, and see the moon crest the horizon through a gap in the octagon at precisely the moon's northernmost rising point - a spectacle that visitors can still see today.

"Every schoolchild in Ohio ought to see this place," says Richard Shiels, history professor at The Ohio State University's Newark Campus. "You come away awestruck that 2,000 years ago, there were people who knew enough to do this, and for some reason cared enough to do this. … The moon rising would only intensify that awe."

Scholars and community leaders are planning an October 22 celebration, dubbed Newark Earthworks Day, in tribute to the moonrise that, while viewable from anywhere, can be witnessed only here in perfect alignment with the earthworks. The celebration begins 12 hours before the anticipated moonrise time of 10:14 p.m., thanks to the combined efforts of Denison University, The Ohio State University and the Ohio Historical Society. Several experts on the mounds, their creators and the astronomy behind them will give presentations at the Newark campus. At the nearby Newark earthwork known as the Great Circle, kids can indulge in an array of outdoor games and demonstrations, while others can learn about the earthworks' orientation to the sky at Denison University's planetarium.

"The more you learn about this site, the more intricate and complicated it becomes," Lepper says, rattling off statistics that show how the octagonal circular and square earthworks are intimately related. Among other geometric phenomena, the distance from the octagon's observatory circle to the circular mound is equal to the distance between the octagon and the square.

Shiels and his colleagues hope the moonrise will catch the public's attention and create what he calls a "teachable moment."

"What's so important is that it isn't just viewed from an archeological or anthropological or native perspective, it's viewed from everybody's - as many everybodys as we can gather - perspective," says Christine Ballengee-Morris, an art education associate professor at OSU Newark and president of the Friends of the Mounds organization. "It allows everybody to see [the native Ohioans'] story and to be able to embrace it in their way."

Another chance to learn about the earthworks comes on November 19, when the Ohio Archaeological Council and the Newark Earthworks Initiative of The Ohio State University will sponsor "Ohio's Ancient Earthworks: A Public Symposium." Also located on the Newark campus, this event features scholars speaking about these ancient wonders and gives the public a chance to discuss ideas or ask questions.

Though today's scientists may never know all the reasons why the earthworks were built here, watching the moon make its lazy ascent from the horizon this month will be the closest anyone has come in years of seeing the ingenuity and splendor of the Ohioans who came before them.