Apostle Islands Ice Caves

In cold winters, Lake Superior freezes solid enough to walk two miles offshore to the Apostle Islands sea caves — sandstone caverns draped in thousands of ice stalactites, frozen waterfalls, and blue-green ice columns. The National Lakeshore only opens the ice cave walk when conditions are safe, sometimes not for years. When it opens, 140,000 people may attempt the crossing in a single weekend.