Updated

Some 4,000 sightseers have been trekking to the Apostle Islands each weekend to see glistening ice caves made accessible by frozen Lake Superior, leading to an unexpected tourism boom in otherwise hibernating villages.

Small businesses in Cornucopia and Bayfield, in far northern Wisconsin, are generally closed for the winter. However, establishments including an inn and general store are staying open to cater to the brisk business, Wisconsin Public Radio reported.

Mike Upthegrove, who runs Ehler's General Store in Cornucopia, generally closes down until April. But because of the surge in visitors he said he'd stay open during the weekend because the ice-cavers need hot drinks and brats.

Down the road, The Village Inn is full and its restaurant is unusually busy, proprietor Cheryl O'Bryon said.

"The last three weekends have been like nothing we've seen before," O'Bryon said. "It is definitely an economic miracle, there's no doubt about that. I'm staffed right now like I would be on the Fourth of July weekend. It's incredible."

She speculated that demand was being driven by earlier visitors who were posting beautiful photos of the ice caves on Facebook.

The caves feature rock formations covered by icy stalactites and stalagmites, giving the space the appearance of a pincushion. And the ice on the lake is so clear in places that the bottom of the lake is visible.

It's fairly rare that the caves are accessible, the Minneapolis Star Tribune reported. It last occurred five years ago.

O'Bryon said she's had customers from as far away as Japan, China and Australia.

The mainland caves are 18 miles west of Bayfield.