Few people realize just how many prehistoric remnants still exist here in the Buckeye State. Ohio is rich with evidence of the ancient American Indian legacy. While many of the earthworks left behind have taught us a lot about these ancient cultures, some of the earthworks remain a mystery. Why they were built and what purpose they served is a fascinating subject to think about.

If you know an Ohio history buff or outdoor enthusiast, the following are 9 fascinating Ohio earthworks that would make excellent day trip destinations for them, the two of you, or a whole crew.

1. Hopewell Culture National Historical Park (Chillicothe)

Ohio ancient mounds abound at Mound City Group in Ross County where you will find the largest collection of Hopewell culture burial mounds in eastern North America, as well as an indoor museum that showcases the Hopewell culture. There's an additional trail along the perimeter of the park you'll want to explore if you have the time.

2. Great Serpent Mound (Peebles)

The largest (and most strangely shaped) effigy mound in the world can be found right here in Ohio in Adams County. The 1,348 ft. long uniquely shaped mound depicts a snake, with an oval shape at its head. Although no artifacts or written records were found near the Great Serpent Mound to determine who built it, a nearby village site shows evidence of occupation by both the Adena and the later Fort Ancient Cultures. The original purpose of the mound remains a mystery, though there is some evidence for astronomical correlations, according to arcofappalachia.org.

3. Fort Ancient Earthworks (Oregonia)

The largest hilltop enclosure in North America can be found in Warren County, above the banks of the Little Miami River. This 126-acre plateau is enclosed by embankment walls that stand about 5 to 23 feet high, which were constructed by the Hopewell Indians by repeatedly dumping baskets of soil on top of one another. Although the exact purpose of the embankment is unknown, archeologists speculate that it was built for ceremonial purposes rather than as a fortress. Today, several research projects still continue ever since remote sensing lead to the discovery of a circular arrangement of posts beneath the ground (commonly known as the Moorhead Circle) in 2005.

4. Indian Mound Reserve (Cedarville)

The 166-acre Indian Mound Reserve in Cedarville features several hiking trails less than a mile, managed by the Greene County Park District. We recommend taking the .6-mile Upper Rim Trail to Cedar Cliff Falls after you've explored these Ohio ancient mounds.

5. Newark Earthworks (Heath)

The largest and most complex set of geometric earthen enclosures in the world were built by the Hopewell between 100 B.C. and 500 A.D., and remnants of these massive earthworks still exist today. In spite of the growth of the city of Newark, three major segments of earthworks are preserved; the Great Circle Earthworks, the Octagon Earthworks and the Wright Earthworks.

6. Marietta Earthworks (Marietta)

This Hopewell ceremonial center is located at the junction of the Muskingum and Ohio rivers in Washington County. Three segments of the Marietta Earthworks are preserved today. Pictured is Conus Mound, which can be found in Mound Cemetery.

7. Flint Ridge State Memorial (Glenford)

Also known as the "Great Indian Quarry of Ohio," these eight miles of quarry pits and high-quilaity flint were used by all of Ohio’s ancient American Indian cultures at one point or another. There is also an onsite museum for visitors to explore and learn more about the archeology and geology of Flint Ridge.

8. Miamisburg Mound State Memorial (Miamisburg)

The Miamisburg Mound is the largest Adena culture burial mound in Ohio and one of the two largest conical mounds in eastern North America. It is 65 feet tall and 800 feet in circumference, and contains 54,000 cubic yards of earth, according to ohiohistory.org.

9. Fort Hill State Memorial (Hillsboro)

Both a Hilltop and Circle Earthwork can be found in Hillsboro. These earthworks were also built by the Hopewell, and can only be seen by hiking the Fort Hill Trail and Buckeye Trail.

Have you ever explored any of these ancient earthworks before? If so, we want to know what your experience was like! And if not, let us know which of these stops you are most excited to visit, or if you plan to visit them all because one simply isn't enough!

For more unique things to see and do in Ohio, check out our list of awesome things to do in Ohio that you can't do anywhere else. There are fourteen spots to check out on this list and each one is more intriguing that the last. From the world's largest basket to a topiary recreation of a famous painting, every type of traveler (or local) will find something they are excited about on this list!