Mendenhall Ice Caves of Juneau in Alaska, United States

The Mendenhall Glacier is a 12-mile-long glacier in the Mendenhall Valley, located only 12 miles from downtown Juneau in Southeast Alaska. Federally protected as part of the Mendenhall Galcier Recreation Area, a unit of the Tongass National Forest, the glacier originally had two names, Sitaantaagu ("Glacier Behind the Town") and Aak'wtaaksit ("Glacier Behind the Little Lake"). 

The Ice Caves are inside the glacier, accessible only to those willing to kayak to, and then ice climb over the glacier. However, the glacier is retreating increasingly fast as global warming heats the oceans and temperatures rise. 

Glass Igloo Village Hotels, Finland

Hotel Kakslauttanen is the home of the famous Igloo Village with the unique Glass and Snow Igloos and the World's largest snow restaurant. In addition guests can enjoy all the other Lappish winter activities including the Northern Lights (Aurora borealis) visible generally from late August to late April. Surrounded by Lapland's exotic and stunning scenery, not only can guests sample the peace of sleeping in snow (the snow muffles sound, and provides a great night's sleep), the glass igloos are fantastic for lying on your bed at night, watching the Northern Lights in the warm.

Pamukkale, Turkey

Pamukkale, meaning "cotton castle" in Turkish, is a natural site in Denizli Province in southwestern Turkey. The city contains hot springs and travertines, terraces of carbonate minerals left by the flowing water. There are dramatic travertine terraces dotted all around the globe, from China to Iran, the USA to Afghanistan. But nowhere else in the world can visitors enjoy exploring both picturesque travertine formations, built up over the millennia from limestone deposited by the abundant hot springs, and the colonnaded streets, temples, bath houses, necropolis and theatre of the remains of an idyllically located Greek-Roman spa city, Hierapolis. You can even bathe, as the Romans once did, in a picturesque pool filled with warm (around 36C), mineral rich waters and swim amongst submerged columns of great antiquity.