In the heart of Phong Nha Ke Bang National Park in Vietnam there is a cave that is rumored to have mythic proportions It has high walls, beautiful rock formations and different environments and is very picturesque.

It was discovered by a Vietnamese man called Ho Khanh in 1991 and was named Hang Son Doong (which is a Mountain River Cave in Vietnamese).

However, it was never fully explored until 2009 when a team of explorers finally went in. The first expedition didn’t make it all the way in. There was in fact a massive wall blocking the descent. This wall was so big that they gave it the name of The Great Wall of Vietnam, a 200-foot wall. They managed to go in just a year later using a special equipment to climb the wall.

Once they got in, the first thing they noticed was the drastic change in temperature. The inside of the cave was very cold due to the altitude and water. The weather inside the cave is completely different from the weather outside. Outside, the weather is a lot hotter and it can be shocking if you go into the cave where it is much cooler. Son Doong is also the largest cave in the world. It is in fact five miles long.

Just to understand better, Niagara Falls is one-third that size. Inside, there’s an incredible jungle, an authentic variety of different ecosystems that have never seen the light of day. How cool is that?