(Missouri)
Graham Cave State Park is a state park in the U.S. state of Missouri consisting of 369 acres (149 ha) located in Montgomery County. The park's namesake, Graham Cave, is a cave in St. Peter sandstone with an entrance 120 feet (37 m) wide and 60 feet (18 m) high and an extent of about 100 feet (30 m) into the hillside. The cave protects an historically important Pre-Columbian archaeological site dating back to as early as 10,000 years ago. Visitors are allowed up to the entrance of the cave where interpretive signs point out significant discoveries. The park includes the 82-acre (33 ha) Graham Cave Glades Natural Area which protects an area of sandstone and dolomite glades with a rich diversity of glade species. The park is adjacent to Interstate 70 from which the entrance to the cave can be glimpsed during foliage-free months. (Ref: https://en.wikipedia.org/wiki/Graham_Cave_State_Park)