Top 10 Largest Underwater Caves

This extensive cave system stretches over 643 miles (1,035 kilometers) in Kentucky, USA. It is the longest known cave system in the world by volume, with estimated depths of up to 350 feet (107 meters). The system contains more than 400 miles (644 kilometers) of underground streams and passageways. Mammoth Cave was named after the abundance of mammoths discovered in the area during exploration. The cave's unique formations have been the subject of scientific study for centuries, with over 150 years of research conducted by notable explorers.

This massive cave is located in Phong Nha-Ke Bang National Park in Vietnam and has a total area of approximately 600 square miles (1,552 square kilometers). It was discovered in 1990 by a local guide named Han Phuc Dung. The cave's massive size can accommodate an entire city, including its own jungle and river system. Hang Son Doong is also known for its unique formations, which include towering ceilings and crystalline structures.

Located in Slovenia, these caves stretch over 9.5 miles (15.3 kilometers) long and feature an abundance of underground lakes, canyons, and caverns. The Skocjan Caves are a UNESCO World Heritage Site and were discovered in the late 18th century by a local geologist. The caves contain numerous formations, including stalactites, stalagmites, and flowstones, as well as a unique 'ice waterfall'.

This cave is located in New Mexico, USA, and has an estimated volume of over 1.3 million cubic meters (46 million cubic feet). It was discovered in 1978 by a group of explorers led by Ron Beckwith. The cave's unique formations include rare geological features such as copper deposits and calcite crystals.

Located on the Georgia coast, this cave stretches over 6 miles (9.7 kilometers) long and reaches depths of up to 1,708 feet (519 meters). It was discovered in 1992 by a group of explorers led by Oleg Sveshnikov. The cave's unique formations include towering crystalline structures and vast underground lakes.

Located in Gabon, these fossilized reactors are believed to be over 2 billion years old. They were formed during the process of nuclear reactions, where natural uranium and oxygen reacted to form uranium dioxide, producing heat. The reactors were discovered by a French team led by Dr. Louis Vanderhaeghe. Oklo Fossil Reactors have significant implications for our understanding of the Earth's early history.

This underwater cave is located off the coast of Iceland and features an abundance of unique formations due to its location near the Mid-Atlantic Ridge. The cave was discovered in 1963 by a group of geologists led by Dr. A. E. J. Goodyear. It contains an array of hydrothermal vent organisms, including giant tube worms.

Located beneath Iceland's largest glacier, this massive ice cave stretches over 12 miles (19.3 kilometers) long and reaches depths of up to 500 feet (152 meters). The cave was discovered in the late 19th century by a group of explorers led by Dr. Einar Axel Gudmundsson. It contains an array of unique formations, including crystalline structures.

Located in Utah, USA, this cave features an estimated volume of over 1.4 million cubic meters (50 million cubic feet). The cave's unique formations include flowstones, helictites, and 'honeycomb' rock, as well as the world's largest column of stalactite crystals.

Located in New South Wales, Australia, these caves stretch over 14 miles (22.5 kilometers) long and feature an array of unique formations, including towering crystalline structures, vast underground lakes, and unique mineral deposits. The caves were named after their discovery by a British explorer named John Hunter in the 19th century.