Tràng An

Where it sits. Tràng An occupies roughly 12,000 hectares of tower karst in Ninh Bình Province, about 95 kilometres south of Hanoi at the southern edge of the Red River delta. The landscape is a dense field of limestone hills, most of them between 150 and 250 metres high, rising abruptly from flooded paddy and channels of still green water. Geologists call this stage of karst evolution the transition from fengcong, where towers still share a connected base, to fenglin, where they stand as isolated peaks on a plain — and Tràng An is one of the clearest places on earth to see both at once. The hills are honeycombed with caves, and crucially many of them are through-caves flooded to water level, so a boat can pass right beneath a mountain and out the other side.

The story behind it. UNESCO inscribed Tràng An in 2014 as a mixed World Heritage site, recognising natural and cultural values together — still Vietnam's only mixed inscription and one of a small number worldwide. The cultural case rests on both deep prehistory and dynastic history. Excavations in the caves have produced evidence of human occupation stretching back some 30,000 years, spanning periods when the sea flooded this basin and later withdrew, which makes it an unusually long continuous record of people adapting to a changing coastline. Much later, in 968, Đinh Bộ Lĩnh unified the country after a period of warlord rule and established his capital at Hoa Lư, in a defensible pocket of these same hills, ringed by karst walls that functioned as ramparts. Hoa Lư served the Đinh and Early Lê dynasties until 1010, when Lý Thái Tổ moved the capital north to Thăng Long, the site of modern Hanoi. The temples of Đinh Tiên Hoàng and Lê Đại Hành still stand on the old citadel ground.

On screen. Ninh Bình's karst carried Kong: Skull Island, the 2017 Legendary and Warner Bros. film directed by Jordan Vogt-Roberts, which shot across three Vietnamese regions — here at Tràng An and Vân Long, at Phong Nha-Kẻ Bàng in Quảng Bình, and in Hạ Long Bay. The production built a village set of thatched huts and totem palisades on the Tràng An waterways, and part of it was left standing afterwards and is now a stop on one of the boat routes, restored and frankly rather tidy compared with the on-screen version. Vietnam appointed Vogt-Roberts a tourism ambassador on the strength of the film, and Ninh Bình's visitor numbers climbed sharply in the years that followed. Earlier, Régis Wargnier used Tam Cốc's river and rice fields for scenes in Indochine in 1992.

What you actually see today. The visit is by rowing boat, and it is the whole point. From the Tràng An boat station, sampans carrying four or five passengers are rowed on circuits of two to three hours by local women, many of whom row with their feet, a technique that saves the shoulders over a long shift. The routes differ: one passes nine caves including Hang Sáng and the long dark Hang Tối, another takes in the Kong village set, a third links a chain of hilltop temples. Inside the flooded caves you duck under stalactites in near darkness with the boat scraping stone. Elsewhere in the complex, Tam Cốc offers a shorter three-cave trip on the Ngô Đồng river, spectacular in late May and early June when the rice below the cliffs turns gold; Hang Múa's 500-odd stone steps climb to a dragon sculpture on a ridge with the best overview of the whole basin; and Bái Đính, a vast modern Buddhist complex begun in the 2000s beside a much older cave pagoda, is the largest temple site in Vietnam and worth seeing for scale if not for antiquity.

Getting there and timing. Trains and buses run from Hanoi to Ninh Bình city in about two and a quarter hours, and the boat stations are 15 to 20 minutes further by taxi or hired motorbike; day tours from Hanoi are common but rushed. Tickets are sold per boat route at the piers, and rowers are paid a set rate with tips expected. March to April and September to November are the most reliable months; winter brings grey drizzle and haze, and July to September is hot with typhoon-season rain. Weekends and Vietnamese holidays fill the boat queues. Boarding a low sampan and the cave headroom make the trips difficult for anyone with restricted mobility, and Hang Múa's steps are steep and unevenly cut.