Ninh BìnhNinh Bình (Tràng An · Tam Cốc · Hoa Lư)

The towers around Tràng An and Tam Cốc are tower karst: the remains of a thick limestone plateau, laid down in a warm sea more than 200 million years ago and dissolved by rain and rivers into steep-sided blocks. Water ran underground, hollowed out passages and then broke through, which is why the boat routes go straight through the hills rather than around them.

Sea levels rose and fell with the ice ages. At the last high stand, about 7,000 years ago, the sea reached the foot of these cliffs, and wave-cut notches and marine shells are still visible several metres above today's valley floor. The landscape is in effect Hạ Long Bay without the water.

Archaeologists have found traces of people in the caves from around 30,000 years ago: hearths, stone tools and piles of shells and animal bones. The record shows how hunter-gatherers adapted as the sea came in and went out again. Several excavated caves, such as Hang Trống, are on the Tràng An boat routes.

The rivers are slow and shallow, fed by springs, which is why the water is clear and why boats are rowed rather than motored. Flow and depth are managed at sluice gates; after heavy rain the caves can flood to the roof, and boats stop.

After independence from China in 938, the country splintered among twelve warlords. Đinh Bộ Lĩnh, a local leader from this area, defeated them and in 968 declared himself emperor of Đại Cồ Việt, with his capital at Hoa Lư. He chose it for defence: the limestone walls formed a natural fortress, and the gaps between them needed only short earth walls.

The Đinh dynasty was short. After Đinh Bộ Lĩnh's murder in 979, the general Lê Hoàn took the throne, married the widowed empress, and beat off a Song Chinese invasion in 981. His Early Lê dynasty ruled from Hoa Lư until 1009.

In 1010 the next king, Lý Công Uẩn, moved the capital north to Đại La on the Red River and renamed it Thăng Long, today's Hà Nội. His edict argued that Hoa Lư was too cramped to be the centre of a growing state. Hoa Lư faded into a village, but the temples to the two founding kings were kept up and rebuilt in the 17th century.

Today you visit the temples of Đinh Tiên Hoàng and Lê Đại Hành, set in the old citadel area, with stone dragons on the steps and statues of the kings inside. Excavations have found foundations, bricks stamped with the name of the kingdom and parts of the palace, some displayed on site.

The flat floors between the karst towers are wet-rice fields, planted twice a year as across the Red River Delta. The spring crop is transplanted in February–March and harvested around late May to June; the summer crop goes in soon after and comes in around September–October. The golden colour in photographs lasts only two or three weeks before each harvest.

Villages sit on the higher ground at the foot of the cliffs, with fish ponds, duck flocks and small family shrines. Many Tam Cốc families row the tourist boats in rotation, a system set up so that income is shared across the commune; that is also why the same boat may be rowed by a grandmother one day and a teenager the next.

Goat meat, grilled or steamed and eaten with rice paper and herbs, is the local speciality, from goats that graze on the limestone. The other is cơm cháy, crispy rice crust fried and topped with a meat sauce, said to have started as a way to use the bottom of the rice pot.

Tourism has changed the valley fast. Homestays and cafés now outnumber farm buildings along some lanes, and the province has tightened rules on building near the protected zone. Staying overnight in a family homestay spreads the money further than a day tour does.

Buddhism came early to Ninh Bình, and cave pagodas such as Bích Động, built into a cliff in the 15th century, make use of the rock itself. The old Bái Đính pagoda is a cave shrine on a hillside; next to it, from 2003, a private developer built the new Bái Đính complex, one of the largest in the country, with long halls of arhat statues and a tall bell tower. Opinions differ on it, but domestic pilgrims come in very large numbers, especially in the first three lunar months.

Festivals follow the lunar calendar. The Tràng An festival is held in the third lunar month, and the Hoa Lư festival in the same season honours the founding kings with processions and reenactments. Visitors in February and March should expect crowds and incense.

Film crews found the valley too. The 2017 film Kong: Skull Island shot scenes around Tràng An and Tam Cốc, and a set of a native village was left standing on one of the Tràng An boat routes. Several Vietnamese historical dramas have used Hoa Lư.

The result is a landscape that is both sacred and staged. A boat trip through Tràng An may pass a restored temple, a cave used by prehistoric people and a film set in the same hour. That mix is typical of how heritage works in modern Vietnam.