In the Big Four Ice Caves (photograph by Michael Matti)

Want to walk in a subterranean winter wonderland? Head to a melting glacier, where the changing of seasons and, many believe, the warming of the planet, contribute to the most ephemeral of secret chambers. In other parts of the world, deep mountain caves are also consumed with ice in strange otherworldly forms. Ice caves, as well as glacier caves, are both under constant change, always prone to collapse, and it’s that dynamic aspect that makes them all the more beautiful.

Here are six of the most stunning ice caves to explore: 

Juneau, Alaska, United States

photograph by AER Wilmington DE

The receding Mendenhall Glacier in Alaska has been gradually melting away, revealing an ancient forest, as well as these gorgeous ice caves. On the interior, water pools in alien-like grottoes and drips over the curved overhangs to create rippling effects like stained glass. It’s just 12 miles from downtown Juneau, but adventurers must first take a kayak and then ice climb in order to experience the temporary wonder. 

Entrance to the ice cave (photograph by Kenneth J. Gill)

photograph by AER Wilmington DE

Detail of the ice (photograph by AER Wilmington DE)

photograph by AER Wilmington DE

Luster, Norway

photograph by Guttorm Flatabø

The Jostedal Glacier in the Nigardsbreen region of Norway is also retreating, and its spectral ice cave was revealed in 2007. Described by some as an “ice cathedral,” it is also in a state of constant flux, with the light from above diffused through its ice ceiling. 

photograph by Guttorm Flatabø

photograph by Guttorm Flatabø

Werfen, Austria

 photograph by Manuel Scheikl

Unlike our first two ice caves, Eisriesenwelt, also known as the “World of the Ice Giants,” is an actual 42-mile limestone cave that curves through the Tennengebirge mountains, formed by a river that flowed through millions of years ago. Only the first mile beneath the surface is filled with ice, though, and before it was discovered in 1879 it was known only to local hunters who feared it as a gate to hell. Now visitors can tour through the ice formations that melt and refreeze throughout the year. 

photograph by Johan Lindgren

photograph by Tak from HK/Flickr user

photograph by Johan Lindgren

photograph by Manuel Scheikl

Leavenworth, Washington, United States

photograph by Michael Matti

The Big Four Ice Caves in Washington are also a bit different from the others on this list as they’re formed from heaps of fallen snow, the caves appearing each summer around late July to August and then remaining as brief portals into October. However, they are incredibly unstable with their packed snow forms, although those brave enough to risk the tunnel collapses are treated to an ethereal gateway. 

Entrance to the caves (photograph by Michael Toyama)

1920 photograph of the cave (via Juleen Studio)

Ross Island, Antarctica 

1978 exploration of the cave (via NOAA Photo Library)

Named by the Robert F. Scott Discovery Expedition that charted its icy land in the early 1900s, the Erebus Ice Tongue in Antarctica is the home of the most remote ice caves on this list. The interlocking frigid chasms are cast in a cool blue light, which gives the ice crystals and stalactites that form in them an otherworldliness right out of a Jules Verne novel. 

photograph by sandwichgirl/Flickr user

via NOAA Photo Library

Westland Tai Poutini National Park, New Zealand

photograph by KristenPGow/Flickr user

New Zealand’s Fox Glacier stretches over eight miles long, and during its century of recent movement elegant ice caves have formed. While the Ice Age-born glacier was once much more giant, it is still an incredible sight, and one that is continuing to transform in contrast to the green valley around it. 

photograph by César González Palomo

photograph by Peter Harmer

photograph by Zak Henry

photograph by anoldent/Flickr user

photograph by Robert Young

photograph by anoldent/Flickr user