Peeking over the eastern horizon, the sun’s light pierces a stand of trees in the distance.

As the sun climbs higher in the morning sky, the trees that tower over Circle Mound catch the light and glow golden and green. With the sun slowly rising higher, the bowing trees and gateway of Circle Mound frame in the sun. For more than 2,000 years the sun has risen in perfect alignment, marking the end of one season and the beginning of another.

For the past four years, I have visited Circle Mound on the spring and fall equinox to see this phenomenon for myself. As a landscape photographer I have traveled all over the country taking photographs of wild and vast landscapes — volcanoes and glaciers, salt flats and dunes — but it was a trip to Mesa Verde National Park in southwestern Colorado where my outlook on landscape photography changed.

Visiting the cliff dwellings and sun temples built by the Ancestral Puebloan people reminded me of the earthwork structures back home. I recalled my visits to Mounds State Park as a child, when I first learned about the Adena-Hopewell people and how they constructed the mounds to use as a gathering place and a sort of calendar that ordered their world. It was not enough to simply photograph these places, now I wanted to capture them in action, functioning as they have for millennia.

Circle Mound is different from most of the other earthworks found in Mounds Park — for one thing, it’s not a circle at all. While it does have rounded corners, Circle Mound is actually rectangular in shape, stretching 285 feet in length and 225 feet across. Surrounded by a 30-foot wide ditch, the central platform of the structure measures 148 feet long and 72 feet wide. The gateway faces due east and was originally flanked by two smaller mounds that have been greatly reduced in size by plowing, as this area of the park was once cultivated. The western end sits high atop a bluff overlooking the White River.

Circle Mound is the only visible rectangular structure of the three discovered in the park. Earthwork G is buried in the campground area and Earthwork F has been severely damaged by cultivation and the construction of a county road. Very little is known about the activities that occurred at Circle Mound and the other rectangular structures. Most of the archeology done at Mounds State Park has occurred at the circular earthworks – the Great Mound enclosure, Fiddleback, and a few small adjacent structures.

Circle Mound sits alone nearly half-mile north of the circular mounds. We may never know how this structure was used by those who built it, but we can always watch the sun rise through its gateway on the equinox and simply enjoy its mystery.

Eliot Reed, an Anderson native, is the owner of Park Place Arts, a custom frame shop and art gallery in Anderson. He is a founding director of Heart of the River Coalition. “On Nature” is published Mondays.