Dark cave is a branch of Phong Nha cave system with the length of 5,558 m and the height of 80 m. It has a primitive beauty with thousands of several spectacular stalagmite and stalactites. Exploring Dark cave is really an amazing experience. We will kayak along Chay river, walk through the dark with with just head torches and plunge into a narrow cavern full of thick, wonderfully gloppy, gooey mud. You will be surprised in front of the beauty hidden in the dark. Inside Dark cave, you will have the opportunity to have a natural mud bath and swim in the cool lake. Besides, you can join many activities such as swimming, zip line, high-wire, and kayaking.