Mysterious underground places worldwide

The Icehotel in Jukkasjärvi is rebuilt every winter from ice blocks harvested from the Torne River. Guest rooms feature ice sculptures and maintain an interior temperature of approximately -5°C. Artists redesign the rooms each year, giving the hotel a different appearance every season.

The Lascaux Cave contains more than 2000 prehistoric wall paintings and engravings created approximately 17,000 years ago during the Upper Paleolithic period. The representations primarily depict animals including aurochs, horses, deer, and ibex, accompanied by abstract signs and human figures. This Paleolithic art site was discovered in 1940 and has been designated a UNESCO World Heritage Site since 1979. To preserve the original paintings, the cave remains closed to visitors, while a detailed replica makes the prehistoric artworks accessible to the public.

Derinkuyu Underground City extends eight levels deep, reaching 85 meters below ground, and provided refuge for up to 20,000 inhabitants during Byzantine times. This tunnel system from the 8th century BC includes living quarters, storage rooms, stables for livestock, churches, wine presses, and assembly halls. Massive rolling stone doors served as defensive barriers against intruders. Ventilation shafts supplied fresh air to all levels, while underground water sources ensured continuous supply during extended periods of occupation.

The Wieliczka Salt Mine stretches across 287 kilometers of underground passages and galleries on nine levels, reaching depths of 327 meters. This mining complex contains underground salt lakes, numerous chambers, and the Chapel of St. Kinga carved entirely from rock salt. Miners created sculptures, altars, and reliefs directly in the salt over centuries of operation. The mine functioned continuously from 1978 through 2013 and is now recognized as a UNESCO World Heritage Site.

Krubera Cave extends 2197 meters into the Earth, making it the deepest known cave system on the planet. Located in the Arabika Massif, this karst formation has been explored through decades of expeditions, with cavers navigating tight shafts, underground rivers, and ice chambers. The cave forms a complex vertical labyrinth of passages and halls carved through limestone.

The Hastings Caves are located in southern Tasmania and offer visitors the opportunity to explore an extensive limestone cave system. The thermal pool within the caves is fed by underground springs and maintains a constant temperature of 28 degrees Celsius throughout the year. The caves formed through the dissolution of dolomite rock over millions of years. Guided tours lead through illuminated chambers featuring stalactites, stalagmites, and other limestone formations.

The Odessa Catacombs form an extensive underground tunnel system stretching over 2500 kilometers beneath the city. These passages were created during the 19th century through limestone mining operations that provided building materials for the expanding urban center. The labyrinth of tunnels and chambers was later used for various purposes, including as a refuge during World War II.

Akrotiri is a Bronze Age settlement on Santorini that was buried by a volcanic eruption in the 17th century BCE. The excavation site reveals multi-story buildings with windows, staircases, and drainage systems. The walls were decorated with frescoes depicting scenes of daily life, animals, and landscapes. This archaeological site lies beneath a thick layer of volcanic ash that helped preserve the structures.

The Catacombs of Kom El Shoqafa comprise three underground levels carved into the rock, forming a necropolis dating from the 2nd century. The site demonstrates the fusion of Egyptian, Greek and Roman artistic traditions in its architecture and decoration. Visitors will find burial chambers, sarcophagi and wall reliefs depicting deities and scenes from different cultures. This archaeological site represents one of the most important Roman burial sites in Egypt.

Chislehurst Caves form an extensive underground network of chalk and flint mines stretching 22 miles beneath the town. These excavations were created over centuries through mining activities that ceased in 1830. During the Second World War, the caves served as an air raid shelter, providing refuge for thousands of people during bombing raids. Today, visitors can explore the winding tunnels and chambers on guided tours, learning about their history as mines, wartime shelters, and cultural venues.

Mammoth Cave National Park protects the world's longest known cave system, with over 420 miles of mapped passages. The limestone caves extend through five levels and contain underground rivers, lakes, and numerous mineral formations. The system developed over millions of years through the dissolution of limestone by rainwater, creating a complex network of chambers and passages today.

Wind Cave National Park protects one of the longest cave systems in the world, with over 150 miles of mapped passages. The cave is known for its exceptional boxwork formations, a rare calcite pattern that represents more than 95 percent of the known occurrences of this geological structure worldwide. The cave system extends through multiple levels with varying air pressure systems that create natural air currents through the entrances, giving the cave its name.

The Jenolan Caves form an extensive cave system within the Silurian limestone of the Blue Mountains. These caves contain underground rivers that have carved limestone formations over millions of years. Scientists discovered fossilized remains of extinct animal species within the passages, providing insights into earlier geological epochs. The cave network extends across multiple levels and features various chambers with different mineral deposits.

The Cave of the Crystals is a natural chamber within the Naica Mine, situated 300 meters below ground level. This cavity houses the largest known selenite crystals on Earth, with some specimens exceeding 11 meters in length and weighing several tons. The crystals formed over hundreds of thousands of years through mineral-rich groundwater at constant temperatures around 58 degrees Celsius. The extreme conditions, including high humidity and heat, limit human access without specialized equipment to brief periods.

The Catacombs of Paris form an extensive network of tunnels and chambers located approximately 20 meters beneath the city streets. These former limestone quarries were converted into an ossuary in the late 18th century when Paris's overcrowded cemeteries posed public health concerns. The bones of over six million Parisians were transferred here and arranged along the walls in geometric patterns. Today, the Catacombs represent an underground monument to mortality, with only a small section open to public visitors who descend through a narrow spiral staircase to explore this subterranean space.

The Waitomo Glowworm Caves form a limestone cave system on New Zealand's North Island, traversed by an underground river. These caves host thousands of larvae of the endemic Arachnocampa luminosa species, which produce a bluish light through bioluminescence. The caves formed approximately 30 million years ago through geological processes and were first explored in 1887 by Maori chief Tane Tinorau and British surveyor Fred Mace. Visitors can explore the caves through boat tours along the underground river, observing the luminescent larvae that adhere to the cave ceilings.

Matmata is a traditional Berber village in southern Tunisia, characterized by its system of underground dwellings. Over centuries, inhabitants excavated vertical shafts into the soft sandstone and created multiple chambers around these central courtyards. This construction method provides natural protection against the extreme temperature fluctuations of the region. Some of these troglodyte homes are still inhabited today, while others have been converted into guesthouses or museums. The village's unusual architecture has served as a filming location for several motion picture productions.

The Edinburgh Vaults form an extensive network of arched chambers built beneath the South Bridge in the late 18th century. These underground spaces served as workshops, storage rooms, and taverns for tradesmen, merchants, and businesses. After several decades of use, the vaults were abandoned due to moisture problems and poor sanitary conditions, falling into obscurity until their rediscovery in the 1980s. Today, visitors can explore sections of these chambers and learn about the daily lives of those who worked in these subterranean spaces.

The Catacombs of Rome form an extensive underground network of passages and burial chambers that originated in the 2nd century. These structures extend over 170 kilometers beneath the city and served as burial grounds for early Christian communities. The tunnels contain numerous wall paintings, inscriptions, and architectural features that provide insight into the religious practices and daily life of that period.

The Kumharwadi Caves were carved from red stone in the 2nd century and served as retreats for Buddhist monks. These underground spaces include several meditation chambers hewn into the rock, along with a central sanctuary. The walls of the main chamber display preserved paintings depicting religious scenes and ornamental designs. The red coloration of the stone gives these caves a distinctive appearance and reflects the local geology.

The Capuchin Crypt lies beneath the church of Santa Maria della Concezione dei Cappuccini and consists of six small chapels. Since 1631, the skeletal remains of approximately 4,000 Capuchin friars have been arranged to decorate walls, ceilings and arches. Bones and skulls form geometric patterns, rosettes and religious symbols. The crypt serves as a memento mori, reminding visitors of the transient nature of earthly existence.

Fingal's Cave sits on the western coast of the uninhabited Scottish island of Staffa in the Inner Hebrides. This sea cave formed through volcanic activity and consists of geometrically shaped basalt columns that extend over 75 meters into the rock face. The cave interior reaches approximately 20 meters in height and becomes flooded by the Atlantic Ocean at high tide. The hexagonal column formations create exceptional acoustic properties that amplify wave sounds and produce echo effects.

The Cango Caves form an extensive limestone cave system in the Swartberg mountain range near Oudtshoorn. These caves contain numerous stalactites, stalagmites, and other mineral formations that have developed over thousands of years. The tunnel network extends more than three kilometers into the mountain and includes several chambers of varying sizes. Visitors can explore the front sections through guided tours, while the back areas feature more demanding passages.

Reed Flute Cave extends 240 meters through limestone formations that developed over millions of years. This cave near Guilin displays stalagmites, stalactites, and stone pillars in various shapes. The interior is highlighted by artificial lighting in different colors, installed since the 1960s. The cave served as a shelter during World War II and takes its name from the reeds growing at the entrance.

The Salt Cathedral of Zipaquirá was constructed within the tunnels of a former salt mine, approximately 200 meters below ground level. The church features three naves carved from halite rock. The Way of the Cross consists of fourteen stations chiseled into the salt walls. The central cross in the altar area reaches a height of sixteen meters. The liturgical spaces utilize the natural pink and gray tones of the salt, enhanced by targeted lighting.

The Karla Caves were carved into basalt rock during the 2nd century BCE and represent some of India's most important Buddhist rock-cut temples. These caves house several prayer halls with elaborately crafted columns, their capitals decorated with elephants and riders. The main hall extends 45 meters into the mountain and is supported by a series of intricately designed stone pillars. The walls feature numerous sculptures depicting scenes from the life of Buddha.

The Longyou Caves form a system of 24 hand-carved chambers cut into sandstone in Longyou County, Zhejiang Province. These underground spaces were created approximately 2000 years ago and cover a total area of 30000 square meters. The caves feature high ceilings, stone pillars, and parallel chisel marks on the walls. Their original purpose and construction method remain unexplained, as no historical records document their creation.