Today the Department of Awesome Natural Wonders reveals an awesomely icy sight that hasn’t been seen since 2009: the Sea Caves found along the Apostle Islands National Lakeshore in northern Wisconsin. The caves are the result of centuries of erosion caused by freezing, thawing, and wave-on-sandstone action that have sculpted the shorelines and they’re only accessible when Lake Superior freezes enough to permit safe passage.

Nature has carved delicate arches, vaulted chambers, and honeycombed passageways into cliffs on the north shore of Devils Island, Swallow Point on Sand Island, and along the mainland near the Lakeshore’s western boundary.

Officials estimate that as many as 1000 people are arriving daily to check out the awesome spectacle of the frozen caves. If the cold weathers holds out, the caves may remain accessible for another month or so.

Via the U.S. Department of the Interior:

Inside the caves awaits a fairyland of needlelike icicles. The formations change from chamber to chamber and from day to day. Apostle Islands is experiencing high volume of visitors right now, so we recommend that you visit the caves during the week. Before heading to the caves, please call the Ice Line at (715) 779-3397 - extension 3, for the most current ice condition information.

Photos by the National Park Service, Kelly Marquardt, and Andy Rathbun respectively.

Head over to Colossal for more images of these stunning caves.

[via io9 and Colossal]