Coral sellers in a boat, Ha Long Bay.Ha Long Bay extends over 1500 sq km of the Gulf of Tonkin at the north-east corner of Vietnam, with over 3000 islands riddled with Karst Limestone Caves. Ha Long Bay was declared as a world heritage site by UNESCO. Legend says Ha Long Bay was formed by a Mother Dragon and her children, sent by the Jade Emperor to protect the Viet from foreign invaders. The dragons flocked from Heaven, spitting out pearls which formed small islands and stopped the invaders and destroyed their ships. Mother Dragon and her children didn't return to Heaven after the battle, but settled into the bay; the Mother Dragon forming Ha Long Bay and the children forming Bai Tu Long.