Coldwater Cave, Iowa's longest and most spectacular cave, is located beneath the gently rolling hills of farm country in northeast Iowa. By far the most significant cave of the Upper Midwest karst region, Coldwater Cave was designated a National Natural Landmark by the U.S. Department of the Interior in 1987. This status is accorded to geologic and ecologic features considered to be of national significance.

Since its discovery in the late sixties, over 17 miles of passages have been documented. The cave system is part of a fluvio-karst drainage basin located in northeast Winneshiek County, Iowa and southeast Fillmore County, Minnesota. The cave proper is situated in the Iowa part of that basin. Formed almost entirely within the Dunleith Formation of the Galena Group (Ordovician), the cave consists of over four miles of borehole and stream gallery, nearly a mile of parallel stream passage and another 11 miles of infeeders and their associated offshoots. The cave system, which is dendritic in its layout, is developed within a subtle carbonate ridge bounded by surface drainages; some of the side passages cross under these drainages. The entire area is mantled with loess and glacial till.

There is only one natural entrance (Historic Entrance) to the cave and it is a water-filled spring that issues from the base of a 100 foot-tall bluff located within the Cold Water Creek Conservation area. Access to the Historic Entrance requires SCUBA and the underwater entrance is currently gated. The system also consists of two other springs and two paleo springs which are not humanly enterable. Primary access to the cave is through a 94-foot shaft (Flatland Entrance) that was drilled by the State of Iowa for researcher access in the early seventies. A second privately owned shaft entrance was drilled in 2003, and is located approximately 1 mile downstream from the Flatland Entrance.