Tien Ong Cave (Grotle du Cieau by the French) is situated on Cai Tai Island, amongst the karst islets population, behind Cua Van Fishing Village in the North of Halong Bay. In 1938, a Swedish archaeologist, Mr J. Anderson, surveyed the remains of the ancient Viet people along the shores and on the islands of Halong Bay and Bai Tu Long Bay, including Tien Ong Cave. Since the findings were announced, Tien Ong Cave has been marked as an important archaeological point on the map representing the distribution of ancient Halong people’s remains.

Source: Internet

The cave entrance has been covered with a layer of emerald green moss due to thousand years of being dipped in sea water that features a primitive charm for the cave right from the first sight. The cave is airy and cool in summer and can avoid cold wind in winter that may also the reasons why ancient Viet people chose this cave to be their home.

Although Tien Ong Cave has officially opened for tourism in 2010, not every cruise in Halong Bay includes it in their cruising itinerary, which makes it not too crowded as other popular attractions on the bay such as Sung Sot Cave and Trong Cave.