Mystery Cave is located about 15 minutes west of the main body of the park, and we headed over there the day after Memorial Day. There weren’t any other visitors when we arrived at 11:00, so we got a personal tour from Antoine, one of the cave guides. There are several different tour options available, but we opted for the easy one-hour tour.
With some 13 miles of passages, Mystery Cave is the longest in Minnesota. The entrance was discovered in 1937, and the cave was operated as a private venture until the state acquired it in 1988. About 20,000 people tour the cave every year, so extra care is taken to ensure that the cave’s ecosystem — including its consistent 48 degree air temperature — isn’t adversely affected.
The one-hour tour was just right for us. We saw some cool things: stalactites, stalagmites, flowstone, and a couple of awesome cephalopod fossils (check out the slide show below). Cephalopods are a member of the family that includes octopus and squid, but the kind that lived in the ocean that covered Minnesota some 450 million years ago had a sort of armor plating.
We also saw several little brown bats, late risers among the 2,000 or so that hibernate in the cave. Because the air in the cave is a consistent temperature, and the cave is obviously dark, each bat relies on its own internal clock to come out of hibernation. One that hibernates every winter near the cave entrance has emerged several years in a row on the same date: June 8.
The visitor center has some nice displays and is well worth checking out. An interesting map shows different points along the South Branch of the Root River where the water flows into the cave formation. At a point just outside the entrance to this part of the park the river disappears entirely, except in periods of high flow, basically taking a shortcut through the cave and re-emerging several miles away.
Pretty cool stuff, and well worth a visit!