These are very old caves. 

These caves are in Australia. 

The Jenolan Caves are in Australia. They are very old. Scientists say they are 340 million years old. This makes them the oldest open cave system in the world. 
A river flows deep under the ground. This river makes many paths through the rock. The caves have over 300 entrances. Inside, you can find beautiful calcite formations. These are shapes made from minerals. Some are pure white. 
You can see fossils in the caves too. These are remains of ancient sea life. Some caves even have bones from animals. 
Many people visit these caves today. Eleven caves are open for tours. They use lights so you can see. The Chifley Cave was the first to use electric light. 
In the Nettle Cave, you can find crayfish backs. These are shapes made by tiny living things. We call these cyanobacteria. They are at least 20,000 years old.
The Jenolan Caves are a huge group of limestone caves in Australia. They are located in the Jenolan Karst Conservation Reserve. This area is in the Central Tablelands of New South Wales. These caves are very special because they are incredibly old. Scientists say they are 340 million years old. This makes them the oldest known and dated open cave system in the world. 
Water is the main thing that makes these caves work. A river flows deep underground through the limestone rock. This river creates many different paths and passages. The cave network has over 300 entrances. Inside, you can see beautiful calcite formations. These are shapes made from minerals that can look pure white. 
People have known about this place for a very long time. The Gundungurra and Wiradjuri peoples have lived near here for thousands of years. They had many names for the area. They even used the underground water for healing. Later, a man named James Whalan found the caves in 1838. He was actually looking for a thief who had stolen tools and clothes. 
Many different people have explored and helped protect the caves. Jeremiah Wilson was the first Keeper of the Caves in 1867. He found many new caves like the Imperial and Jubilee caves. In 1884, the name Jenolan Caves was officially used. The Chifley Cave was very special because it was the first cave in the world to use electric light. This happened all the way back in 1880. 
You can see many amazing things if you visit today. There are eleven show caves that are open to people. One cave, the Temple of Baal, has a huge 9-metre shape called the Angel's Wing. You can also find fossils from ancient sea life in the rocks. In Nettle Cave, you can see crayfish backs. These are shapes made by tiny living things called cyanobacteria.
The Jenolan Caves are an extensive network of limestone caves in Australia. They are located within the Jenolan Karst Conservation Reserve. This reserve sits in the Central Tablelands of New South Wales. The caves are located west of the Blue Mountains. They are also west of Sydney and east of Katoomba. These caves are incredibly significant to science. They are the oldest known and dated open cave system in the world. 
Scientists have determined the age of these caves through complex geological methods. They measured the ratio of radioactive potassium to trapped argon gas. This gas is produced when potassium decays over long periods. By studying the clay in the caves, they found it is 340 million years old. This makes the system a major site for geological study. The Commonwealth Scientific and Industrial Research Organisation (CSIRO) leads much of this research. They work with the University of Sydney and the Australian Museum. 
The cave system functions through the movement of water. A subterranean section of the Jenolan River flows through the network. This water carves out multi-level passages over millions of years. The network contains more than 300 different entrances. Inside, visitors can see beautiful calcite formations. These mineral structures can sometimes appear pure white. The caves also contain numerous Silurian marine fossils within the bedrock. 
Indigenous peoples have known this area for thousands of years. The Gundungurra and Wiradjuri peoples have deep cultural ties to the land. They used various names for the area, such as Binomil or Bin-oo-mur. A Gundungurra Dreamtime story describes the creation of the country. It involves a struggle between two spirits: Gurangatch, an eel-like creature, and Mirrigan, a large native cat. The Gundungurra people even used the subterranean water for healing. They believed the water held curative powers for the sick.
European discovery of the caves happened in the 1830s. Most accounts credit James Whalan with the discovery in 1838 or 1841. He was actually pursuing a thief named McKeown who had stolen livestock and tools. James reported the find to his brother, Charles Whalan. Charles later conducted visitors to the caves in the 1840s. In 1866, the NSW Government took control of the site. It became the second area in the world reserved for conservation. 
Many different caves have been discovered by early keepers. Jeremiah Wilson was appointed the first Keeper of the Caves in 1867. He discovered the Imperial, Jersey, and Jubilee caves. Later, J. C. Wiburd discovered five more caves, including the River and Orient caves. Some caves are famous for specific features. The Chifley Cave was the first in the world to use electric light in 1880. The Temple of Baal features a massive 9-metre shawl called the Angel's Wing.
Today, the Jenolan Caves are a major tourist destination. There are eleven illuminated show caves open to the public. The Jubilee Cave is the longest show cave, though it is the least visited. The Orient Cave was the first in the world to be cleaned in 1968. Scientists found that steam cleaning could damage crystal formations. Now, they use water from the underground rivers for cleaning instead. The area is also part of the UNESCO World Heritage-listed Greater Blue Mountains Area. 
The caves are also important for studying ancient life. Nettle Cave contains "crayfish backs." These are stromatolites shaped by cyanobacteria, light, and wind. These formations are estimated to be at least 20,000 years old.
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