Dong Hang Hanh tunnels through mount Quang Hanh 9 km from the township of Cam Pha. The tunnel and cave is approximately 2 km in length.
To visit this cave the visitors must take a small row boat to access the entrance. On the way the rower must maneuver through a variety of rock formation often so narrow that only one boat can fit through at
a time.
The air in the tunnel is several degrees cooler than the air outside. As one proceed deeper into the cave, the surroundings become more mystifying as the rocky walls take different shapes, sizes, and hues. Hang Hanh contains many formations. One formation takes the form of a drum (for water) called Ang gao. One looks like a temple with millions of diamond-like crystals as its outer layer. There are several columns of rocks that look like remnants of buildings from some ancient world. These monoliths are several stories high. Theres also a formation of a natural amphitheater in the middle of the water with smaller formations in place as the audience.

Ao Tien or Pond of the Nymphs, was named by the locals because it was rumored this is where the nymphs gathered to take a bath. The limestone walls surrounds this part of the ocean creating a natural pond in the middle of the bay. Ao Tien is located in an island with a lagoon-like setting, surrounded by limestone walls, accessible only by small row boats and only in low tides. During high tide, the water rise to cover the opening and keep the water here clean. The water in Ao Tien is only chest deep and very warm. During low tide visitors can disembark from the bigger boat and use a row boat to enter Ao Tien. Some visitors even swim through the opening without using a boat. Many tourists use Ao Tien as a place to sunbathe and wade.