EDMONSON COUNTY, Ky.—A storm rolling through Kentucky on Sunday left behind quite the eerie sight at Mammoth Cave National Park.

The storm caused a quick drop in temperature and filled the Rotunda room with a dense fog, according to the National Park Service.

Photos posted to the national park’s Facebook page show the fog sitting inside of the cave.

Mammoth Cave National Park is located in Kentucky, just over five hours south of South Bend.

The national park is home of the world’s longest known cave system. It also earned the title of UNESCO World Heritage Site.