Sung Sot Cave

In the middle of Ha Long Bay lies Bồ Hòn Island, less than 4 square kilometers in size. On it is a cave whose name sounds like a soft cry slipping out of someone's mouth. The French called it Grotte des Surprises, which means the Cave of Surprises. The Vietnamese name is shorter, and truer too: Sửng Sốt Cave. In Vietnamese, sửng sốt means stunned with amazement.

At first the name sounds odd, because a cave is hardly a place for surprises. Every cave is dark and cool, with water dripping somewhere in the rock. And yet the French found this cave in 1901 and gave it that name, and the name has stayed with it ever since. The surprise can wait a little. First comes the slow way in.

The way to the cave begins on the water. The boat leaves Ha Long International Cruise Port and travels about 11 kilometers. It weaves between limestone islands that rise straight out of the sea. UNESCO recognized this bay as a natural World Heritage Site in 1994, then recognized its geology and landforms as well in 2000. Among hundreds of islands, Bồ Hòn appears, green and quiet. It looks no different from the islands around it.

The cave mouth does not sit at the water's edge. It is up on the side of the island, about 25 meters above sea level. To get in, visitors climb steep stone steps. Along the path grow the familiar trees of the bay. Near the entrance there are two kinds of fig tree, called si and sanh. There is fragrant bauhinia, and there are vines hanging down the rock face. From the entrance down to the foot of the island grow cluster figs and Ha Long palms. There are plants called giềng and bông mộc, and there are begonias.

But the plant most worth stopping for is the Ha Long cycad. It is endemic to the bay, which means it would be hard to find anywhere else in the world. On the cliffs in front of the cave, these cycads grow close together, several hundred of them. They cling to the limestone in clusters, like a silent guard that has watched over the cave door for years beyond counting.

Then comes the step through the entrance. The sunlight of the bay falls away behind, and the air turns soft and cool. The first chamber is already wide. People often compare it to a grand theater inside the rock. From the ceiling, stalactites hang down in clusters. Under the lights they glitter, each with its own shape, so strange that it is hard to stop looking.

No one carved these stalactites, and no one sculpted them. Rainwater seeps through the limestone, carrying a little mineral with it, then falls drop by drop. Each drop leaves a layer so thin that the human eye cannot see it. One year, ten years, a hundred years, and then far longer than that, those thin layers pile up and become stone.

Deeper in, the path suddenly narrows. The two main chambers of the cave are joined only by a narrow passage. It is so narrow that the cave seems about to end.

And then the second chamber opens up.

The ceiling soars to about 30 meters. That is roughly the height of a ten-story building. The space is vast and covered in stalactites, and the lamps throw a glow across the walls like stage lights. Here, perhaps, the riddle from the start of the story finds its answer. The whole cave covers about 10,000 square meters. It is the largest limestone cave open to visitors in Ha Long Bay. A hollow that vast lies hidden inside a small island, behind a narrow passage. Anyone who steps through that passage comes out sửng sốt, stunned with amazement.

In the great chamber, many of the stalactites have shapes that call familiar things to mind. People say this one looks like a sword and that one like a horse. One spot resembles a dinosaur, another a banyan tree, another a fur seal. These are names that visitors and guides made up for fun. They are not official names.

A folk legend tells of Saint Gióng, a hero credited with defending the country from foreign enemies. After he defeated the enemy, the legend says, he left his horse and his sword in this cave. What is certain is simpler, and more wonderful too. It was the small drops of water that shaped every one of those forms.

The cave also has tiny residents that spend their whole lives in the dark. There are cave spiders and cave bugs, creatures at home without light. In the small pools on the cave floor lives the Ha Long cave crab, a crab found nowhere but this bay. Scientists consider it very valuable for conservation and research.

For almost a century after the French named it, the cave lay quietly on the side of the island, closed to visitors. Only in 1993 did Sửng Sốt Cave welcome its first visitors. That was exactly one year before UNESCO recognized Ha Long Bay. In 2012, an association of Czech travel agencies and tour operators voted it one of the ten most beautiful caves in the world. At its busiest, the cave receives about 2,000 visitors an hour. They file one after another through that narrow passage.

Leaving the great chamber, visitors follow a small stone-paved path to the exit. Outside, the light of the bay rushes in, dazzling white after the darkness of the cave. From up high, the whole of Ha Long Bay spreads out like a painting. There is wide water, and limestone islands follow one another to the horizon. Tiny boats are bringing people in and carrying people away.

From up there, it is hard to believe that the small island below holds a whole theater of stone. Inside, deep in the rock, the drops of water are still falling, one drop and then another, preparing a surprise for the people who will come later.