Explore Caves
It's not surprising that Halong Bay has a lot of caves given the number of cliffs and mountains there; Driftwood Island is a great location to explore and find something interesting.
Two caves may be found on this small island to the southwest of Halong Bay: the massive Thien Cung cave and the tall but shallow Dau Go grotto. The entrance to Dau Go cave, for instance, is "only" 12 meters high, but the highest dome within reaches 25 meters tall and is covered in stone pillars and stalagmites. Both caves are at least two million years old and feature several remarkable chambers. Three ponds are located inside Thien Cung Cave, which is also illuminated with vibrant lights, which creates a dancing of ghostly images on the walls as visitors walk by.