Root River and bluff in Preston, Minnesota. Photograph by Wikimedia Commons user Jonathunder, May 27, 2006. GNU free documentation license.

Bluff seen from the north branch of the Root River in Olmsted County Park, south of Simpson, Minnesota. Photograph by Wikimedia Commons user Jonathunder, 2017. GNU free documentation license.

Mystery Cave passageway at Forestville Mystery Cave State Park, an example of caves formed from having karst topography. Photograph by Wikimedia Commons user McGhiever, July 27, 2013. CC BY-SA 4.0.

A view of a bridge spanning the Root River in Fillmore County, Minnesota, ca. 1940. Limestone bluffs are visible above the river and bridge.

Highway 9 in the Root River Valley showcasing limestone bluffs outside of Lanesboro in Fillmore County, Minnesota. Photograph by Mathias O. Bue, ca. 1930.

Limestone bluffs along Lynch Creek southeast of Chatfield in Fillmore County, Minnesota, ca. 1900.

Trees jut out from a karst sinkhole in a field near Harmony in Fillmore County, Minnesota. Photograph by Amy Jo Hahn, 2018.

Trees jut out from a karst sinkhole in a field near Harmony in Fillmore County, Minnesota. Photograph by Amy Jo Hahn, 2018. Used with the permission of Amy Jo Hahn.

Aerial view of sinkholes outside Fountain in Fillmore County, July 3, 2011.