Cathedrals of ice: 16 must-see photos of the Superior caves

Single digit temps greeted visitors Thursday.
Single digit temperatures, a chilly wind and fresh ice formations greeted visitors to the Apostle Islands National Lakeshore ice caves Thursday, March 5.
Derek Montgomery for MPR News

Single digit temperatures, a chilly wind and fresh ice formations greeted visitors to the ice caves of Wisconsin's Apostle Island National Lakeshore on Thursday, March 5, 2015.

The ice caves were only open for nine days this season and the National Park Service warned of treacherous and slippery ice conditions the entire time.

Due to deteriorating ice conditions park officials closed the caves for the winter on Monday, March 9.