A farmer saw a hole in a mountain. But what was inside stunned the whole world

There is room to put a 40 floors skyscraper in it, and it contains a jungle and a river. The Son Doong caves in Vietnam are the world's largest and a tour inside them is something unusual.

Join us on a wonderful journey in a parallel world under the ground.

The huge cave is located in Vietnam's Phong Nha-Ke Bàng National Park about 450 km south of Hanoi.

The meaning of "Son-Doong" is a cave-shaped mountain, formed about 2 million years ago. But it hasn't been discovered for a long time. The cave was first discovered in 1991 by local residents, but the first people to study it were British researchers in 2009.

The entire length of the cave is about 140 km.

It contains its own animals, rain forest, lakes, beaches, and river.

Many caves have memorabilia and signs from prehistoric times such as sculptures and frescoes, but nothing that looked anything like this has ever been found in the cave.

In 2013 the first tourists visited the cave.

There are guided tours to get there. The tour takes about a week and costs around $2,300. At this price you will establish a camp within the cave for 5 days.

The cave also contains rare pearls that have been shaped for hundreds of years by droplets of water that dried and formed a layer of lime on the sand.

Here's a video on the cave: