In 1944 Halong Bay in Northern Vietnam was designated a UNESCO World Heritage Site in recognition of its unique geological significance. Three hundred million years earlier Northern Vietnam, and the place that is now Halong Bay, were under a shallow sea dotted with coral reefs. For the next 100 million years the discarded shells of marine organisms accumulated to form a massive slab of limestone more than 1,000 metres thick. According to geologists this limestone was uplifted by tectonic forces and sculpted by monsoon rains into the dramatic karst topography of the Bay.
But there are other explanations. According to Vietnamese mythology a great dragon charged out of the mountains and as it entered the sea its thrashing tail carved out the myriad islands. And it is mythology, not science that gave the place its name – Halong means “where the dragon entered the sea”.
It’s about a three-hour drive from Hanoi to Halong City (aka Hong Gai), a small port town at the entrance to Halong Bay. Most of the route is across the Red River delta, an utterly flat landscape of rice paddies, fields of corn, and vast areas flooded with shallow water. This incredibly fertile farmland yields two or three crops a year and the fields are crowded with people both harvesting and planting. We are almost three hours into our drive when the first rounded summit of a karst mountain appears in the distance. A few kilometres farther the horizontal landscape of the delta changes abruptly to the vertical landscape of the coast.
Located on the northern shore of the Gulf of Tonkin, Halong Bay bristles with almost 2,000 steep-sided islands and sea-stacks. Their rounded summits and near vertical walls are typical of karst mountains throughout the world but their marine location makes them scientifically special and scenically stunning. Karst topography results from the slow solution weathering of limestone by slightly acidic rainwater and, since limestone is not soluble in sea water, karst is formed only above sea-level. And that’s what makes Halong Bay so unusual. Its islands have a history of tectonic ups and downs that has taken them from the ocean to dry land and back again to the sea.
Halong Bay’s World Heritage status and spectacular scenery have made it one of the busiest tourist destinations in Vietnam. Hong Gai harbour is a veritable armada of junks tied several abreast to the dock and anchored in clusters offshore. Fitted out for both day- trips and overnight tours they are tended by a flotilla of smaller craft, mostly open rowboats, that scurry among them like water beetles in a lily pond. After many enquiries we located our boat and climbed aboard for a two day cruise through the Bay.