Bright Cave - Dark Cave is located in the area bordering Lan Ha Bay and Ha Long Bay, in the protected area of the Biosphere Reserve of Cat Ba archipelago. This is an ideal destination for those who love kayaking, discovering nature when traveling to Halong and Cat Ba.

Bright Cave - Dark Cave is regarded as the underwater Sung Sot Cave because the formation of the cave is not on the water like other caves. In the process of geological activity, there are 3 types of caves in Halong Bay formed from the impact of water to karst topography, which are remnants of old phreatic caves, old karstic foot caves, and marine notch caves. Bright Cave - Dark Cave belongs to the form of marine notch caves with the cave floor lying deep in the sea water, while the ceiling is on the water surface.

With a kayak, visitors can get closer to the foot of the rocky mountain, discover the beauty of nature, the fun of water erosion at the foot of limestone, as well as the bravery of plants which survive in this rocky terrain.