Until a few years ago, the world's largest cave - over 5.5 miles long and nearly 500 feet high in some places - wasn't even known to exist. Comprised of an entire wonderland, the cave boasts a brand new plant species, fields of algae, cave pearls and an entire river all hidden from human eyes deep underground. Now tourists can explore the cave, declared one of the most beautiful in the world by the BBC, and see this natural wonder for themselves.
The cave, dubbed Son Doong Cave (Hang Son Doong in Vietnamese), which means mountain river cave, is located in the Quang Binh province of Vietnam.
A full-sized river runs throughout the 5.5 mile cave, from which the cave takes its name.
For the past few years, only explorers have been allowed to enter the ecologically sensitive area, which requires a bit of rappelling to get into.
The cave is over 5.5 miles long and nearly 500 feet high in some places, big enough to fit an entire city block, buildings included, inside.
A local farmer stumbled on the cave in 1991, but he didn't go in because the entrance he discovered had an extreme drop. The cave wasn't explored until 2009 when a group of British explorers led by Howard Limbert finally went in.
Tourists will be allowed to enter the cave for the first time next year, led by a company called Oxalis. Only 220 permits will be issued for visitors.
The cave's roof has collapsed in some places, allowing plants to grow and wildlife to flourish. Scientists have even discovered a previously unknown species of plant.