The Trinh Nu Grotto or Virgin Grotto is situated on the island range of Bô Hon in the system comprising the Sung Sôt Grotto, Dong Tiên Lake and Luon Grotto. It is 15 km south of Bai Cháy Beach. For fishermen, the Virgin Grotto is their house, but for young lovers, it is considered as the symbol of truly love, and is the romantic place for taking oath of love.

Situated in the centre of the UNESCO-declared World Heritage area, the Sung Sôt or Surprise Grotto is on Bo Hòn Island, and is one of the finest and widest grottoes of Ha Long Bay. From the wharf, you climb 50 steep stone stairs to the mouth of the grotto, which lies 25 m above the sea level. Going down some 10 stone stairs, you reach the mouth of a grotto. The grotto covers some 10,000 m2.

Legend has it, that beautiful young lady named Mây (cloud), caught the eye of the Dragon Prince and he fell in love with her. They were betrothed, and their wedding lasted seven days and seven nights in the very centre of the grotto.

am Cung Grotto lies in Mây Ðèn, a luxuriant island nearly isolated from other islands. Mây Dèn’s cliffs are extremely vertical, while its forest is flourishing.situated in the centre of Ha Long Bay, 5 km from Sung Sôt Grotto to the northeast. The grotto itself is divided into three parts; after threading the stone cracks, you find the first chamber. Many beautiful forms can be garnered from the rocky shapes..

Two kilometers south-west of Ti Top Beach is the Mê Cung Grotto or Bewitching Grotto. It formed on Lom Bò Island, and seen from afar, the entrance is like the roof of a house denting the island’s side.

Visitors will be carried by small boats to visit Luon Glotto. The small boats are controlled by the sailors of boat who have been experienced in these small boats so that travellers can enjoy the scenery of islands surrounding the cave. Many visitors choose to kayak into the cave and travellers on the boats often say "Hello!" with friendliness. the feeling of being relaxed creates unforgettable impression left in travellers' mind...