Today US ABC make a live broadcast of a Good Morning America featuring a Vietnam's natural wonder

[BoQ77]

Vietnam's Mammoth Cavern - Interactive Graphic - National Geographic Magazine

 

[biendong]

It's not expensive if you know there're 3 supporters who accompany you and make sure your trip safe and harmless to the cave. They also cleanup everything you left inside.

yes, price is increased to 3.000 US$ now and we have to wait for end of 2016.

 

[Skull and Bones]

These kind of caves generates it's own micro weather system, and it's own ecology. Government should be strict on maintaining the natural balance of these habitats, as these giant caves are home to unique species of plant and animals.