Thirteen miles of mapped passage under the bluff country make this the longest cave in Minnesota, cut by the Root River through 450-million-year-old limestone. It holds a constant 48 degrees and has deep blue pools that mirror the ceiling. The state park offers both a lit hour-long walk and a lantern-lit scenic tour. PUBLIC, Forestville/Mystery Cave State Park, Preston.
Other places on the map within a couple of hours.
