Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Cold Water Spring State Preserve is a 60-acre parcel state preserve protecting a spring that issues from Cold Water Cave, an extensive cave system in Winneshiek County, Iowa and Fillmore County, Minnesota. The spring is a tributary of the Upper Iowa River. The cave system contains a large underground creek that courses around much of the cave's nearly 16 miles of passages. The cave system has some unusual features such as its rate of expansion, which is higher than that of most caves. It also has relatively low amounts of oxygen and high amounts of carbon dioxide. The cave is a National Natural Landmark, designated in 1987.