The Underground Forest was still standing as of 2013 when the photos below were taken. The place closed in the 1960's after Old 27 gave way to I-75. The attraction and the adjacent house were purchased by a family intent on keeping the structures intact. However, I think they are gone (as of 2021) due to being beyond repair.
The folks were nice enough to show us around and they allowed us to take pictures. Just inside the entrance was a ticket office, souvenir shop and concession stand. The remainder of the structure was built into a hillside. Beyond the souvenir shop was a series of underground tunnels featuring dioramas with various taxidermy animals on display that were indigenous to the region. Evidently some of the animals can still be seen at the Call of the Wild attraction in Gaylord. They were moved there after the Underground Forest closed down.
There were also smaller displays which showed movies. Many thanks to the owners who took the time to share this rare artifact of mid century tourism. We would ask that anyone visiting the area not trespass on the grounds of the Underground Forest as it is now private property. There is construction going on and walking around inside could be hazardous.