Our guide points to the crone seated just inside the doorway, grinning toothlessly at us. "See that old lady? She's 90." Ancient as she is, the amazing "house that is a village" we have just entered is far older. In fact, some of its doughnut-shaped earthen buildings were built as long as 700 years ago, by Mongolian refugees who, after many years of searching, chose to settle in the fertile valleys of China's Fujian Province.
Here, in these impregnable rammed-earth houses topped with black terracotta tiles, life began again. At an altitude of 800 metres, the cool climate was perfect to grow cabbages and persimmons, tea and turnips. Little did they realise that, centuries later, their unique architecture would almost spark an international incident.
In 1985, with the Cold War still front and centre, these strange square and ring-shaped structures looked sinister enough on the US surveillance satellite to rattle the White House. After all, they were hidden in valleys directly inland from Taiwan. The US government sent in spies to check out the "group nuclear base".
Today, there is a smooth new highway to Yongding from Xiamen, a tourist island and bustling city on the coast south of Shanghai. Delightfully relaxed and dotted with lakes and waterways, Yongding is one of China's smaller cities, with a population of just 5million. It is almost within sight of Taiwan. In fact, you can just see one of the archipelago's outlying islands a few kilometres offshore.
By coach, it is a comfortable four-hour trip. But the US investigators had to trek in over mountains to see and photograph the evidence - only to leave swiftly, embarrassed.
If our welcome was anything to go by, on entering each "reactor" they would have been offered a cup of green tea, while the only weapons they would have found were knives and cleavers used to dispatch chickens and pigs for the cooking pot. The clay courtyard of the four-storey earthen fortresses would have been filled with fluffy yellow ducklings, toddlers and people going about their daily business.
Warfare was the furthest thing from the minds of these peaceful inhabitants.
To visit a "tulou", 46 of which were added to the UNESCO World Heritage list last year, is to step through a portal into another culture, another time. Big enough for up to a thousand people, each "house" is a complete village, usually accommodating an entire clan .
Outside, on concrete slabs, chillies, corn, mushrooms, persimmons and rosellas are drying in the sunshine, while slender heads of cabbage hang on a fence.
As we clamber up the shaky stairs from the ground floor, which is reserved for communal activities, past the second floor used for storage to the accommodation level, I feel for the elderly who have yet another staircase to manage - inexplicably, the fourth (and top) floor is reserved for them.
Downstairs, we sample some of the locally grown tea and marvel over a bottle of strong spirit filled with enormous bumblebees. "Drink it. Good for the knees!" we are exhorted. Maybe we'd need to if we had to manage those stairs every day.
Then came an offer too good to refuse.
Hokkien (Hakka) is the cuisine of Taiwan, though it is perhaps better known as a staple in the hawker food of Singapore and Malaysia. Many Chinese emigrated en masse from Fujian Province in the 19th century - ironically because of famine - and their simple peasant dishes, rich in soy sauce and duck, became the foundation of the popular "nonya" food, which grew out of the intermarriages with Malays.
We lunch in a small room outside the tulou. The plates come constantly: eggplant and red hot chillies, pork belly bathed in oily turnip broth, sweet potato chips dusted with sugar, fried whitebait, cold poached duck - all fried, all delicious and, finally, all too much.
You could be forgiven for thinking the original builders of the tulou were themselves frustrated chefs. To form the metre-thick walls, local red soil was first mixed with sand and stone and then glutinous rice, brown sugar and egg whites, making a mix stronger than concrete, even before it was reinforced with bamboo.
The balconies that run along each floor create an atrium overlooking the central area. Most tulous were built with a single gate, for security, and had a source of water inside, as well as waste disposal. Often a temple stands in the centre, for these people brought their Confucian and Daoist beliefs with them.
There are so many tulous in the area - the more elaborate ones date from the 17th and 18th centuries - that you could spend days exploring them. We visit another one in a delightful village called Taxii. Here, while there are some tulous, most people live in almost European-style houses overlooking the water.
In the late afternoon as we stroll along the path beside the river, we nod and smile at the locals seated outside their homes, smoking and relaxing with their families. Occasionally, we step aside for a cyclist, or a farm truck returning home, and once a shiny black sedan pushes importantly through.
In this remote part of China, it seems ludicrous to imagine satellites and nuclear reactors. But then to people who build with brown sugar and egg white, maybe not.
The writer travelled as a guest of Helen Wong's Tours.
TRIP NOTES
Singapore Airlines flies from Sydney to Shanghai 24 times a week. Fares start from $811 plus taxes. Yongding is a four-hour coach ride from Xiamen. Helen Wong's Tours (02 9267 7833, see helenwongstours.com) has a six-day Fujian Province tour from April, for groups of two or more, for $1650 a person, twin share, land only.
Overnight, before the tour starts, Central Hotel Shanghai. It's adjacent to the Nanjing Road Pedestrian Mall. See centralhotelshanghai.com.
See travelchinaguide.com/cityguides/fujian.
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