This section is an extension of the Bluegrass Region of Kentucky that extends into most of Adams County with smaller portions in the extreme southeastern parts of Brown and Highland counties. This small triangular-shaped area is characterized by ancient, reddish-yellow, calcareous soils, and deep valleys carved into easily erodible shale often capped with more erosion resistant limestone and dolomite rims which form massive steep cliffs such as Buzzardroost Rock. These alkaline soils which were never glaciated are among the oldest in the state. The Bluegrass Region is also characterized by sink holes, small caves, rock crevices, and numerous Red Cedar Barrens prairie openings. Although several of the same prairie species found growing in the glaciated Till Plains grow here as well, the prairies of the Bluegrass Region are believed to predate Wisconsinan glaciation. Many of the rarest prairie species found growing here are more typical of the Cedar Glades of the Missouri Ozarks. Two of the best such prairies are Lynx Prairie and Chaparral Prairie Nature Preserves. Plants rare to Ohio and more characteristic of the Carolina Mountains can be found growing on the dolomite cliffs and boulders. In the narrow, cool and moist dolomite gorges, several northern or high altitude mountain species such as Northern White Cedar can be found. The oldest White Cedars in Ohio grow in Cedar Falls Nature Preserve and are believed to be at least 300 years old. Because of its diverse landscape which supports relict plant colonies of North, South and Western origin, the number of rare state listed species of plants found growing in the Bluegrass Region is second only to those occurring in the Oak Openings of Northwestern Ohio. At the northern tip of this region the most fascinating geological feature in Ohio, the Serpent Mound Meteor Crater or Cryptoexplosion Structure occurs. This is a five-mile circular area where the bedrock is out of sequence, older rock on top and younger rock at the bottom, as if this site had been struck by a huge meteorite. It could have been a meteor strike millions of years ago or something else. Scientists are still not certain.