Son Doong cave is now known as the World's Largest Cave. Son Doong cave (200 meters wide, 150 meters high, and at least 6.5 kilometers long) is much larger than Deer Cave in Malaysia, currently considered the world’s largest, an explorer said (Deer Cave is 90 meters wide, 100 meters high and 2 kilometers long). It is located in located in Son Trach, Bo Trach District, Quang Binh province, Vietnam. The cave is located near the Laos-Vietnam border. It is found by a local man named Ho Khanh in 1991 and was recently discovered in 2009 by British cavers from the British Cave Research Association, led by Howard and Deb Limbert, conducted a survey in Phong Nha-Ke Bang from April 10-14, 2009. The biggest section of Son Dong is five kilometers in length, 200 meters high and 150 meters wide, said Howard Limbert of the British Cave Research Association team. It is believed that it was created 2-5 million years ago by river water eroding away from the limestone underneath the mountain Where the limestone was weak, the ceiling collapsed creating huge skylights. The name "Son Doong" cave means "mountain river cave"

The most surprising fact about this cave is that it is not discovered by geologists, scientists, or any professional but it is discovered by a local hunter in a rainy day. He was looking for a shelter to hide from a tropical downpour. Ho Khanh, a farmer, and huntsmen were on his journey for a jungle game in 1991. He accidentally found the mouth of the cave when he was looking for a shelter from the rain. He didn't recognize how big his discovery was and he almost forgot it. The British Caving Association got informed by Ho about a cave hidden in the jungle when they came to explore the karst system in the area in 2009. Members of caving association, with the help of Ho, faced real difficulty in re-finding the cave mouth as i is located in the deep forest which in on a very difficult terrain and unsearchable with google earth. They got deep inside, measured things, collected data, taking pictures and a giant natural wonder was revealed.

The average width, height and length of Son Doong Cave is 150m , 200m, and 5 km respectively while the second placed cave, the Deer Cave on Malaysia, is only 150m wide, 120m high and 2km in length. There is enough room for a 40 storey building at one place in the cave where the height is measured at 243.84m. These dimensions are recorded by the British Caving Associations explorers and they observed that the length of the cave can be much more that this as no one has yet reached the end due to technical and equipment limitation.