Puong Cave is located in the Nang River of Ba Be district, Bac Kan province. It is about 5km from the Cha Ra town. The Puong Cave attracts visitors with its strange and unique stalactites and the bat community of ten thousands. The Nang River flows under the limestone among the vertical cliffs of Lung Nham Mountain that is Puong cave. The small boat floats in the cave with the ethereal lights. Beside this magical scene with color and sound of water and light, visitors would be fascinated by the strange stalactites in the gate of the cave. There is a community of bat inside the cave with the number of tens of thousands. On the east north of Ba Be Lake, in the hillside of the Lung Nham range, Puong cave is one of the favored destination with the height of 50m. It creates a splendid entrance with the Nang river flows for 300m through the cave, which creates one of the most magnificent limestone landscapes of Ba Be national park. The cave is the residence of many night creatures. Typically, there are 18 types of bats with the amount of thousands, which covers the vast number of national park of Ba Be. They often run in the twilight and dawn time. There are three types of bat, which are important in pollination, and distribution of the seed. The bats, which eat insects, also help with protecting the local crops from many harmful insects. However, the noise for visitors and bothering for local people to gather its dung are affecting the down number of bats.
Souce: http://indochinaexplorertour.com/en/travel-blog.nd625/puong-cave-near-by-ba-be-lake---bac-kan-province---viet-nam.i315.html