Here are some of the most stunning images of the world's grottoes and caves:
This amazing natural grotto pool in Texas was created thousands of years ago due to the collapse of the dome of an underground river. Among the most striking features of this beautiful pool is a 14 m (45 ft) waterfall, spilling from the dome.
By Frank Jaquier
Hamilton Pool. By DaveWilsonPhotography
Slovenia is home to impressive Škocjan Caves, one of the world's largest canyon hidden deep underground. This outstanding formation is considered a natural phenomenon of global significance, ranking side by side with the Grand Canyon, the Great Barrier Reef, or the Galapagos Islands.
Skocjan Caves. By StrudelMonkey
By Kalense Kid
Underground Pools in Škocjan Caves. By Hannu Salama
Patagonia's Glacier Caves
Far at the southern tip of Argentina, Patagonia is home to amazing Parque Nacional Los Glaciares , where the world's most impressive glaciers can be found. Among one of the most stunning ice formation are the glacier caves that have been formed by water running through or under the glacier. Such caves can also be seen in Iceland, Alaska, Norway and New Zealand.
Ice Cave, Glacier Grey. By Tom Holub
Delicate rare limestone formations make the Lehman Caves one of the most wonderful underground chambers on the globe. Located in the Great Basin National Park, Nevada, USA, the cave was discovered in 1885 by Absalom Lehman.
Only 13 km from Kuala Lumpur, the capital of Malaysia, there are Batu Caves, an outstanding complex of chambers and grottoes housing Hindu temples. The caves are formed by limestone which is believed to be 400 million years old. The main feature of the complex is a 100 m high open vault called the Cathedral Cave.
Batu Cave. By Stuck in Customs
Waitomo Glowworm Caves
The tiny creatures inhabiting Waitomo Glowworm Caves in New Zealand are the complex's main tourist magnet. These unique glittering cave animals called Arachnocampa luminosa lit up the interior of the limestone complex, making it an absolutely extraordinary location.
Reed Flute Cave
Located in Guilin City in China, the Reed Flute Cave, also called the Palace of Natural Arts, is 240 m long cave network discovered some 1,200 years ago. This scenic complex of karst caves is filled with amazing stalactites, stalagmites, and stone pillar formations of many different shapes and sizes, which, enhanced by multicolored lighting, form a one-of-a-kind underground world.
Crystal Lake, Reed Flute Cave. By Cheddarcheez
Hang Sung Sot
Hang Sung Sot, or the Cave of the Surprises, is one of the most amazing caves in Halong Bay in Vietnam. The two chambers that form this amazing grotto are decorated with thousands of spectacular stalactite and stalagmite forms. The cave was discovered by the French in 1901.