On the south-east side of Ha Long Bay, about 25 km from Bai Chay Wharf, Cong Do is in Bai Tu Long Bay in the region which recognised as the World Heritage. It has an area of 23, 363 sq. m, and its mountain reaches a peak of 172 m. The island features many lagoons, which are the residence of numerous species of sea-life, such as shrimp, crab, fish, squid and aquatic plants. On the south-west side of the island, there is a wide coral reef displaying a myriad of colours.

This island consists of three small mountains with the height of 23 m, seen from afar, resemble three peaches (Ba Trai Ðao). The island connects to a legend of about the romantic love between a youngest fairy who was very pretty with a young and poor fisherman.