For the first time in five years, visitors to Lake Superior's Wisconsin shore can experience the winter beauty of the Apostle Sea Caves—completely frozen and safe to visit, thanks in large part to this winter's exceedingly low temperatures. National Park Service officials, who monitor conditions along the Apostle Islands National Lakeshore, say that the last time Lake Superior's ice was thick enough to safely hold visitors to the caves was back in 2009; but with weeks of frigid temperatures caused by the polar vortex, Lake Superior has iced over enough to support adventurers on their one-mile trek from mainland Wisconsin out to the caves.

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Bob Krumanaker, Apostle Islands National Lakeshore superintendent, told Wisconsin Public Radio that the caves are one of the most unique sites in the park, which includes 21 islands formed from sandstone over a billion years ago.

Visitors to the caves who make the mile-long trek over an icy lake are greeted by an amazing winter view, with icicles hanging like stalactites from the cave ceilings and a clear ice floor that reveals the lake floor below. During the summer, visitors can kayak through the caves, but a solid lake offers adventurers the only way to experience the caves on foot.

On a peak weekend day, more than 1,000 people can visit the caves. Krumanaker hopes that weather conditions will allow the ice caves to remain visitable for another six weeks, though with fickle winter, the caves could be closed as soon as the coming weekend. If you can't venture out on Lake Superior to check out the caves firsthand, we've compiled some of Instagram's best to give you a sense of the icy beauty.