Transcript for Experiencing the beauty of Vietnam's Ha Long Bay

Finally tonight here, a magical spot, about 100 miles from where we are here in Hanoi. Kim Jong-un's grandfather came to see it in the 1960s. And not long ago, we saw it for ourselves. We head out to the chopper waiting in Hanoi to take us to a breathtaking sight. The crew is about to show us a place some 100 miles from Hanoi. We take off for ha long bay, and in the air we begin to see what draws millions from all over the world. "Ha long" means "Descending dragon." And looking out the window, the incredible sight. The limestone formations as far as we could see. And from the ground, the tour boats dwarfed by those formations. It really is spectacular. I mean, everywhere you look here, you see the limestone islands coming out of the water. Take a look at this. They estimate that there are thousands of them here in the bay. It was not long ago ha long bay was named one of the new natural wonders of the world. And they are very proud here. Ha long became one of the seven new wonder natural of the world. Because you see that here not only the view. View very, very beautiful view. Ha long became one of the seven new wonder natural of the world. Reporter: Unesco has placed ha long bay on the world heritage site. 18 years, you've been a tour guide. Right. So you know this place well? Of course. Ha long is my hometown. Reporter: Scientists believe these formations began 500 million years ago, sculpted by techtonic movement and ocean water. Why the mountain goes up? That means that happened by earthquake but happened very, very long time ago. But now we see here very, very peaceful. Very beautiful view here. Reporter: A place where millions on tour boats still share the waters with the local fishermen and their families who call ha long bay home. Feel very lucky to have seen it myself. Thought we'd share it with you tonight. And thank you for watching here on a Tuesday night. I'm David Muir. I hope to see you right back here tomorrow night from Hanoi. Until then, have a good evening.

This transcript has been automatically generated and may not be 100% accurate.