Top 5 Longest Cave Systems in the World

Located in Kentucky, USA, the Mammoth Cave System is the longest known cave system in the world, stretching approximately 643 miles (1,035 kilometers) underground. This extensive network of passages was formed over millions of years through a combination of limestone dissolution and volcanic activity. With over 400 miles (640 kilometers) of explored passages, it's estimated that the full extent of the system is at least twice as large. The cave system was first mapped in 1791 by a group of local explorers.

Located in Phong Nha-Ke Bang National Park in Vietnam, Son Doong Cave is the second-longest known cave system in the world, measuring approximately 379 kilometers (235 miles) in length. This massive cave was formed when the Phong Nha Cave collapsed into a rift caused by tectonic activity. The cave features its own jungle ecosystem and is home to unique species such as the Son Doong fly frog, found nowhere else on Earth. Son Doong Cave was officially declared the world's largest cave in 2013.

Located in Palawan, Philippines, the Puerto Princesa Subterranean River is often considered a single cave system, but it does form part of the larger Agusan Cave System, which stretches approximately 225 kilometers (140 miles) in length. The river itself flows through an underground karst channel and features stunning limestone formations and unique geological structures. This site was designated as a UNESCO World Heritage Site in 2011 due to its exceptional natural beauty.

Located in central Vietnam, theHang Son Doong is one of the largest caves in the world, stretching approximately 150 kilometers (93 miles) in length. Its unique shape is thought to have been formed by volcanic activity and tectonic processes, creating an enormous cavern with its own weather patterns, forests, and even river systems. This discovery sparked international attention due to its relative remoteness and lack of human impact.

Located on the Black Sea coast in Georgia, the Krubera Cave is a massive limestone cave system stretching approximately 120 kilometers (75 miles) in length. Due to its extensive network of passages and chambers, explorers believe that it may contain undiscovered species or ecosystems unique to the region. The cave's history dates back millions of years, with initial mapping taking place in the late 19th century, but much of its full extent remains unexplored.