Halong Bay is in the Gulf of Tonkin off Haiphong, the fourth largest city in Vietnam. It is a stunning environment dotted with 1600 islands comprised of limestone which rise precipitously from the emerald waters. The conical and columnar limestone structures are known as karsts. The area achieved UNESCO World Heritage Site status in 1994. The UNESCO website describes the reason for the beautiful and unique landscape thusly: "The geomorphology of Ha Long Bay is known as a drowned karst landscape due to the exceptional combination of its limestone karst features which have been subject to repeated regression and transgression of the sea over geological time. The limestones of Ha Long Bay have been eroded into a mature landscape of fengcong (clusters of conical peaks) and fenglin (isolated tower features) karst features, modified by sea invasion at a later stage."
A more romantic explanation for the awesome landscape is given away by the bay's name, Ha Long, which means descending dragon. Legend has it that the 1600 limestone karsts were formed by jade jewels spit from the mouths of a family of dragons sent by the gods to protect Vietnam from northern invaders.