The most prominent feature of the state park is the large sinkhole formed by the dissolution of limestone by acidic groundwater over long periods of time.

In the summer, the bottom of the sinkhole is dramatically cooler than the air at the surface due to the depth and shade from the canopy above.

In the sandhill environment, the sandy soil and regular fires result in pine trees being the predominant vegetation.

However, the Millhopper was often used by students as a place to socialize and have parties, which led to problems with litter and erosion from foot traffic.

[3] The site was purchased by the state in 1974, and a set of 236 wooden steps, along with boardwalks and an observation deck at the bottom were completed in 1976 to allow access to the sink for visitors without further soil erosion.