The Hang Son Doong Cave is located in Phong Nha-Ke Bang National Park, Vietnam and broke the record for worlds biggest cave. This massive cave is also known as "cave of the mountain river," and has it's own jungle, river and lakes.

Hang Son Doong was discovered in 1991 by a local Vietnamese logger named Ho Khanh when he stumbled upon the cave to find cover from a storm. Khanh describes hearing a whistling sound of wind while out on his walk which is what led him to the discovery of the the largest cave in the world. After he returned home he sought out to find the cave again, and finally re-discovered the giant cavern in 2009 with the help the British Cave Research Association.

Researchers surveyed the cave using laser measuring devices. The cave runs for approximately 5.6 miles and in some areas measures more than 460-by-460 feet (140-by-140 meters). Two large sections of the cave, called Dolines, are collapsed. The sunlight they have allowed in the cave has resulted in the growth of lush rainforest. A river runs through the entire cave. It's current eerily rushes into the darkness and can be heard echoing throughout the whole cave system.

Hang Son Doong is now open to the public by a company called Oxalis and they offer a six day trip for visitors. It has only been open since 2013 and tours sell out extremely fast, creating two year long waitlists. In order to explore Son Doong Cave you must hike for a day and a half through dense jungle and then rope down a 260ft wall.

It is amazing to imagine that there may be even bigger cave passages left to be discovered around the world.