Ha Long literally means descending dragon(s) and according to local myth, the story goes as follows:
Long ago when their forefathers were fighting foreign invaders from the north, the gods from heaven sent a family of dragons to help defend their land. This family of dragons descended upon what is now Ha Long bay and began spitting out jewels and jade. Upon hitting the sea, these jewels turned into the various islands and islets dotting the seascape and formed a formidable fortress against the invaders. The locals were able to keep their land safe and formed what is now the country of Vietnam. The Dragon family fell so much in love with this area for its calm water and for the reverence of the people of Vietnam that they decided to remain on earth. Mother dragon lies on what is now Ha Long and where her children lie is Bai Tu Long. The dragon tails formed the area of Bach Long Vi known for the miles of white sandy beaches of Tra Co peninsula.
This myth is in line with the Vietnamese myth of their origin Con Rong Chau Tien. This myth describes the union between a king (representing the dragon) and his bride (representing a goddess) giving birth to 100 children which are the ancestors of the Vietnamese people. The Ha Long myth illustrate the Vietnamese belief of their origin and the fact that throughout their history, they are aided by their ancestors, the dragon and the gods, in the defense of their land.
Scorched Beach (Bai Chay)
Upon arriving in Ha Long city, the visitor will be driving along 'Bai Chay' or scorched beach. The sand on this stretch of beach is dark. And judging by the name the visitors may mistakenly think that this is due to the dry climate or lack of wind in this area. However, contrary to this interpretation, the area is quite pleasant during the summer and fall months and the temperature here is around 70 deg F. According to the locals, Bai Chay got its name long ago, based on another historical event. Bai Chay was once a forest. In 1287, the Mongols led by the great Truong Van Ho,(a Vietnamese name for this Mongolian general) attacked Vietnam and was driven back by general Tran Khanh Du. Many Mongolian ships were set afire and drifted to shore aided by high wind setting the forest on fire. Since then this stretch of beach became known as Bai Chay or scorched beach.
From Bai Chay, visitors can hire a boat and go out to the bay. It is here that visitors will be find some of Southeast Asias most fascinating sites. Visitors to the bay speak highly of its almost mystical qualities and the surrealistic scenery that defines this bay. The limestone formations are both bizarre and awesome. Over thousands of years the base of many of the formation have corroded 
to a point where many seem to be balancing on thin air. The shapes and the positioning of these formations often resemble people, animals etc., hence, most are given a name by the locals. Some of the more famous are: Hang Dau Go ( Wooden Stakes cave), Hang Bo Nau (Pelican cave), Hang Trinh Nu (the Virgin), Hang Sung Sot (Cave of Awe), Dong Hang Hanh, Dao Tuan Chau (Sentinel Chau Island), Qua Chuong (the bell), Con Voi (the elephant) etc.. Now, about one thousand formations have names. One can't possibly see all of Ha Long grandeur in one day or even a month since depending on the time of the year, the weather, or the condition of the bay the visitor may see only one small aspect of Ha Long's beauty.
Hang Dau Go (Wooden Stakes Cave)
Hang Dau Go is one of the most beautiful cave at Ha Long. The name, Dau Go or Giau Go, has direct ties to the history of Vietnam. According to the locals, while preparing for the Mongolian attacks in 1288, general Tran Hung Dao, sent a convoy to this area to cut wood from this region. Wooden stakes were then fashioned from the wood and hidden in Dau Go cave. The stakes were embedded in Bach Dang river to form a barrier against the attacking Mongols. According to legend, general Tran Hung Dao dealt a great blow to the Kublai Khan when he tricked the Mongolian army into chasing him deep up Bach Dang's channel. When the tide were down the enemies were stuck in these wooden stakes driven into the river bed. Dau Go was also the site where general Tran Khan Du hid his force while waiting for the Mongols led by Truong Van Ho in 1287.
Dau Go is located on a limestone islet 8 km south of Bai Chay. The islet itself stands 187 m above sea level. Upon arriving visitors must hike the 90 rocky steps that lead to the cave's entrance. There are three chambers with the outer one having the most spectacular stalagmites and stalactites. Some are as tall as 20 m in height. The locals claim that these giant formations resemble human forms and are the keepers or guardians of Dau Go cave. The outer chamber is also the largest with capacity for three to four thousand people. The cave's floor is approximately 6 m lower than the entrance and the distance from floor to ceiling is approximately 25 m.
The middle chamber is accessible through a narrow passage approximately 1.4 m wide. There is a round crystal like structure on the path. When struck by light, this structure emits a kaleidoscope of light that is both breathtaking and unique. The inner chamber is famous for the colorful stalagmites and stalactites.
The inner chamber is much smaller by comparison. It is here that visitors will find stone wells filled with fresh water. According to the locals these wells are filled year round.
Dau Go is probably the most famous of all grottoes in Ha Long. Since its discovery, many Vietnamese dignitaries have visited Dau Go cave. In 1929, King Khai Dinh (Nguyen dynasty) visited Dau Go cave and was awed by its beauty. His praise in writing is carved on a stone stele at the entrance of the cave.