Ancient as she is, this amazing "house that is a village" which we have just entered is far older. In fact some of these doughnut-shaped earthen buildings were constructed as long as seven hundred years ago, by refugees from Mongolia who had trekked far south in China looking for the ideal spot to re-establish their communities. After many years they chose to settle in a series of fertile valleys in Fujian Province.

Here in their impregnable rammed earth houses topped with black terracotta tiles, life began again. At an altitude of 800 metres they discovered that in this cooler climate they could 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, at the height of the Cold War, these strange square and ring-shaped structures looked sinister enough to the KH22 US surveillance satellite to rattle the White House. After all, they were hidden in valleys directly inland from Taiwan. The US government's response was immediate. They sent in spies to check out the "group nuclear base".

Today there is a smooth new highway to Yong Ding from Xiamen (once known as Amoy) an island at the mouth of the Nine Dragon river. Today a delightfully relaxed city with lakes and waterways, it is one of China's smaller cities, with a population of just five million. It is almost within sight of Taiwan. In fact you can just see one of the archipelago's outlying islands just a few kilometres offshore.

By air-conditioned coach it is a comfortable four-hour trip. But the intrepid US investigators had to trek in over mountains to see and photograph the evidence - only to leave again swiftly, embarrassed.

If our welcome was anything to go by, on entering each "reactor" they'd have been offered a cup of green tea, while the only offensive 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, just as they are today.

Warfare was the furthest thing from the minds of these peaceful inhabitants.

To visit a "tulou", one of 46 added to the UNESCO World Heritage list last year, is to step through a portal into another culture, another time zone. Big enough for up to a thousand people, these "houses" are complete villages, and usually accommodates an entire clan.

Outside, on concrete slabs, chillies, corn, mushrooms and persimmons - and amazingly, rosellas, the red buds we make jam out of in Australia - 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 ("see, no windows," our guide points out) to the accommodation level, I feel sorry for the elderly who have yet another staircase to manage. Inexplicably, the top, fourth floor, is reserved for them.

Downstairs, we sample some of the locally grown tea, and marvel over a bottle of strong spirit filled with the most enormous bumblebees we have ever seen. "Drink it. Good for the knees!" we are exhorted. Maybe we'd need to, we reckon, if we had to manage those stairs every day.

Then came an offer too good to refuse.

Hokkien (Hakka) food is the cuisine of Taiwan and also the Chinese food of Singaporean and Malaysian hawker food. Ever eaten hokkien mee noodles? Many emigrated en masse from Fujian province in the 19th century, ironically because of famine. Their simple peasant dishes rich in soy sauce and duck, became the foundation of the popular "nonya" food which grew out of the intermarriage of these Chinese with the local Malay people.

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. Interesting ingredients were used to form the metre-thick walls. The local red soil was first mixed with sand and stone, but then glutinous rice, brown sugar, even eggwhites were added, making a mix stronger than concrete, even before it was reinforced with bamboo.

The balconies that run along each floor create an atrium effect overlooking the central area, and add to the sense of community. Most tulous were built with a single gate, for security in case of a siege, 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 Taxii, a delightful village, its river crossed frequently by narrow arched bridges. Here, while there were some tulous, most people live in almost European 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 is as though time has stood still. To imagine satellites and nuclear reactors in this context seems ludicrous. But then to people who build with brown sugar and egg white, maybe not!

Trip Notes

Getting there: Singapore Airlines flies from Sydney to Shanghai around three times daily (24 times a week). Adult return current specials (available until 31st March) start from $811 + approx. $612 taxes/charges (fluctuates with the currency until ticket issued).

The tulous of YongDing are about a four hour coach ride from Xiamen, a tourist island and bustling city on the coast south of Shanghai.

Helen Wong's Tours (www.helenwongstours.com) will be offering a new six-day Fujian Province tour from April 2009,  year-round, for groups of two or more. The tour cost is $1650 per person, twin share, land content only, all accommodation and most meals included. It can also be added to other Helen Wong's Tours.

Stay overnight before the tour commences adjacent to the Nanjing Road Pedestrian Mall, at Central Hotel Shanghai, www.centralhotelshanghai.com

More information:

Fujian Province: www.travelchinaguide.com/cityguides/fujian/

Helen Wong's Tours: 02 9267 7833, www.helenwongstours.com