The popular ice caves on Lake Superior near the Apostle Islands are now closed, concluding an unprecedented wave of tourism and exploration.
The National Park Service says the caves along Lake Superior were closed just after midnight Monday. The park service says the ice was getting too weak to support foot traffic to the caves, which are accessible by kayak in the summer.
Park service spokeswoman Julie Van Stappen says 138,000 people visited the caves this winter. That figure dwarfs the 12,700 people who visited in 2009, the last time the lake froze enough to make the caves reachable by foot.
When the ice caves were inaccessible in 2012, there were 6,700 people who visited the park.
Van Stappen says this season's attendance was "amazing."