Ho Dong Tien (Fairy Lake Cave) is one of the most beautiful caves in Halong Bay. Due to its special values of geology, geomorphology and formation history of Halong Bay, Ho Dong Tien so far is reserved for the environmental ecology classroom (Ecoboat) and specialists for researches only. Ho Dong Tien has a typical structure of veranda caves, with the cave bottom a little higher to the sea surface, even with a portion of the entrance immersed into the sea water and must be fortified to be easily gotten in.

Ho Dong Tien Cave

With a glance, Ho Dong Tien is not special and in a tide, sea water covers a third of the entrance. There is an entrance fit a person to get in only. The difference lies within: On the ceiling, stalactics falling down beautifully sparkling. Ho Dong Tien has relics of many cave bottoms on the walls which form the “lofts” drawing long. According to scientists, these are parts of the cave with relatively solid formations of CaCO3 which have been eroded by flows of groundwater occured over thousands of years.

If studied in details the remains of the cave bottoms, the process of rising and lowering the sea water level of Halong in the Fourth Era (lasted about 2 million – 1.6 million years ago) could be discovered. It is a great significance to the restoration of geologic history of the area. The cave now has many stalactites columns hanging down touched the ground, as a basis to predict that under the current cave floor also existing an ancient cave ground. It is a mystery not yet discovered.

Ho Dong Tien Cave

Especially in the dense darkness, no wind blowing, crabs, spiders, crickets are still living fine. How have they born and feed is still a mystery. From the second compartment of Ho Dong Tien cave, there are two doors out to a lake, surrounded by limestone mountains. They call this type of lake “ponds” but in fact this is a karst funnel with a submerged bottom. It has a special ecological environment, while isolating in the sea but with circulated underground system and cracks in the limestone. So that there usually has been a unique biota within and may consist many endemic species.

The fact that the management board has not allowed to bring tourists into the cave, helps keep the stalactites in natural state. The stalactites here seem to fully display their magical glitter. Million of calcite crystals gleamed magically when met a mild light that in such exploited caves as Sung Sot (Surprise Cave), Thien Cung (Heaven Palace Cave), Dau Go (Hidding Wood cave) have gone forever..