Photos by Cheryl Landes

The Mima Mounds is a mystery. No one knows for sure how the bumpy landscape originated in these 637 acres of prairie grasslands. Theories are abundant, from pocket gophers excavating nest chambers to permafrost cracking near the end of the Ice Age.

What scientists know for sure is that the mounds were formed some time after the Ice Age glaciers began retreating more than 16,500 years ago. Meltwater from the glaciers flowed over the ground and deposited gravel and rock. The gravel outwash became the well-drained, dry soil of the prairie.

The mound heights range from one to seven feet, and the widths are from eight to 40 feet. The landscape reminds me of a the bumps on a sheet of bubble wrap laid flat, except the bumps are covered in grass and occasionally support a tree or two. Lichen grows in patches along the trail.

The trail starts at the picnic area next to the parking lot. From there, stop at the Interpretive Center, a concrete structure shaped like the mounds, to read about the natural history of the area. Climb the stairs to the top of the center for a panoramic view of the preserve.

At the Interpretive Center, the trail splits into the North Loop, a half-mile flat dirt trail, and the ADA Loop, a half-mile paved loop. If you continue straight, you’ll pass another viewing platform on the right and can continue to the South Loop or veer left to explore a small forest.

The trail through the forest reconnects to the ADA Loop and the trail to the picnic area.

In the fall, the prairie turns a light golden color and the leaves on the oak trees change. Butterflies flutter, birds sing or fly high overhead, and deer graze. Often I see deer during my walks there.

The National Park Service designated the mounds as a National Natural Landmark in 1966, and 10 years later, the Mima Mounds Natural Area Preserve was established. The preserve is among 17 landmarks in Washington State.

The preserve is located at 12315 Waddell Creek Road SW in Olympia, Washington. Hours are 8:30 a.m.-8:30 p.m. April-September and 8:30 a.m.-5:30 p.m. October-March.

A Discover Pass is required. Passes are $10 per day or $30 per year (buy online).

Dogs are not allowed at the preserve, except service dogs.

For more information and directions, visit dnr.wa.gov/MimaMounds. I recommend printing out the directions, because cell reception can be spotty in this area.