The Ice Palace on top of Europe, Switzerland.

Tunnels of ice polished as smooth as cut glass lead through the so-called Ice Palace at Jungfraujoch, which offers a frosty reception at minus 3°C. Mountain guides wielding saws and pick axes carved the chambers out of solid ice in the 1930s.

Jungfraujoch is an underground railway station situated below the Jungfraujoch col in the Bernese Oberland region of Switzerland. At 3,454 meters (11,332 ft) above sea level, this is the highest railway station in Europe, and is close to the summits of the Eiger, Jungfrau and Mönch mountains.

https://en.wikipedia.org/wiki/Jungfraujoch

https://en.wikipedia.org/wiki/Jungfraujoch_railway_station

https://www.lonelyplanet.com/switzerland/jungfraujoch/attractions/ice-palace/a/poi-sig/1575206/1329104

http://grindelwald.net/index.php?userlang=en&page=jungfrau