Ice Cave Near The Mutnovsky Volcano, Russia - Ice caves like these form in the glaciers surrounding the Mutnovsky Volcano in Russia. Some of them are formed by vents that release volcanic heat and gases called fumaroles. (photo by Florian Wizorek)
Glowworms Cave, New Zealand - The Waitomo glowworm caves are home to a unique insect – the glowworm. These insects hang glistening silken strands from the ceiling of the cave and glow to attract unsuspecting prey. (photo by waitomo.com)
Son Doong Cave, Vietnam - This is the largest currently known cave in the world. It is filled with countless wonders including isolated ecosystems, weather systems and geological formations. (photo by National Geographic)
Batu Caves, Malaysia - These caves have been used by English and Chinese settlers as well as the indigenous Temuan people. The bat guano in the cave was mined for agricultural purposes, but now the cave is filled with statues and is open to visitors. (photo by Danny Xeero)
Marble Caves, Patagonia - Theses caves are known for the spectacular reflections that the turquoise water casts on the white marble ceiling of the cave. They are also called the Marble Cathedral because of their beautiful and arching forms. (photo by kellywhite)
Phraya Nakhon Cave, Thailand - This cave was historically a popular visiting place for local kings because of the illumination provided by the collapsed roofs. The pavilion in the center was built for the visit of King Chulalongkorn in 1890. (photo by Wasitpol Unchanakorrakit)
Ellison’s Cave, United States - This photograph is of the Fantastic Cave pit, part of Ellison’s Cave in the state of Georgia. It is a popular attraction for pit cavers – those who enjoy rappelling down vertical subterranean drops. (photo by secondglobe.com)
Vatnajokull Glacier Cave, Iceland - This cave is located in the largest glacier in Europe. Caves like these form due to melting glacial icewater, but they can be dangerous because glaciers are constantly breaking and changing. (photo by Einar Runar Sigurdson)
Cave in Algarve, Portugal - Due to its location, the cave is prone to various seaside formations because of the rock face’s relative solubility in water. This specific cave near Lagos is accessible only by water. (photo by Bruno Carlos)
Reed Flute Cave, China - The Reed Flute Cave in Guangxi, China has been visited by tourists for at least 1200 years. The cave is home to a spectacular array of stalagmites and stalactites. It is named for the reeds that grow at its mouth, which can be made into flutes. (photo by Pasquale di Pilato)
