Ha Long Bay, 165 km east of Hanoi, is located at the centre of the offshore area of Quang Ninh Province. It is one of the natural marvels. The deepest place is not more than 200 metres. The area of the bay's surface is 1500 km2. There are thousands of vegetation-covered islands with diverse shapes which are rising from the clear, emarald waters of the bay. There are a lot of grottoes such as Hang Dau Go (Grotto of Wooden Stakes), Bo Nau, Trinh Nu Cave