POSEN, Mich. (Michigan Back Roads) – The sign at the trailhead reads “Mystery Valley.” The valley contains one of the largest karst “collapse valleys” in the entire Great Lakes region. The collapse is due to the limestone bedrock dissolving in water and results in sinkholes and enormous cracks in the earth. The “mystery” part of the name comes from the fact that this valley cycles between being full of water, sometimes more than 20 feet deep, and being bone dry. From 2016 to 2021 the water was nearly 30 feet deep. Then, it suddenly drained away and remains dry into the fall of 2022. The name is a throwback to a misguided commercial enterprise.

The story goes that a local real estate developer, Art Poch, who had an idea back in the 1950s. He had seen the water drain out of the main lake through a sinkhole. Sometimes it drained so fast that a whirlpool would form as the water began the long journey to Lake Huron. Mr. Poch figured that he could blast that sink drain open making it possible to enter the caverns below, and people would pay to visit the caves deep under ground. There was the additional attraction of an abundance of prehistoric fossils on a nearby hill. He even planned to build a carillon to fill the mile long valley with music. It was an awesome vision, but things didn’t go quite as planned. The enterprise failed quickly and all that remains is the chimney for a fireplace at a picnic spot and a hiking trail.

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The trail is an interesting walk, especially if you know the history of the valley. It winds through a mixed forest of pines and hardwoods so it’s quite beautiful during color tour season. Along the way you encounter cracks in the bedrock, some of which are rumored to be more than 100 feet deep. The cracks are often filled with debris so it’s difficult to determine their actual depth. There is a scenic spot where you can view the dry lakebed. The trail loops around and you end up back at the parking area in about half an hour. If you are travelling in northeast Michigan near Posen, this is cool spot to stretch your legs.