The brutally-cold temperatures are causing ice to form in the Apostle Sea Caves.
For the first time in five years, you can visit the Apostle Islands sea caves in far northern Wisconsin by walking across frozen Lake Superior.
Apostle Islands National Lakeshore superintendent Bob Krumanaker said the experience of walking on a frozen Great Lake is remarkable, both physically and psychologically.
The mainland caves are 18 miles west of Bayfield. With the current conditions, the National Park Service said the caves are a "fairyland of needle-like icicles," according to a Wisconsin Public Radio report.
Krumanaker said there are beautiful rock formations covered by icy stalactites and stalagmites. He says if you crawl under them, the ice is like a glass floor through which you can see the bottom of the lake.
He said he hoped the caves would be open for six weeks, but said wind and weather could change that as soon as Saturday.