Standing before the huge circular building, it is plausible to think you have been transported back in time.

The structure standing in a mountainous area of East China's Fujian Province, is circular and made of compact mud.

It is a tulou, which literally means "a big building made of soil."

Developed for more than 1,200 years, the buildings are now scattered in areas dwelled by Hakka people, who migrated from ancient Central China between the 5th and 13th centuries to the junctures between Jiangxi, Fujian and Guangdong provinces in the east and south parts of the country. At its peak, a tulou often sheltered 20 to 30 homes belonging to one big family.

Yongding, a county in western part of Fujian Province, has most - about 8,000 tulous. Zhencheng Building, located in Hongkeng Village in Yongding, is the most famous among them.

"Our ancestors were soldiers sent by the central court to conquer local robbers, so they built the castle-alike building," Lin Xiaohong, a 20-year-old resident in the Zhencheng Building, told China Daily.

Lin makes a living catering to tourists.

According to Lo Hsing-lin (1906-78), a famous professor of Hakka history, the people's legend to brand their ancestors as generals or soldiers is because they have experienced many fights and frustrations.

Since the Jin Dynasty (AD 265-420), the Hakka have been moving southward from northern Shanxi and central Henan provinces due to the nomadic invasions.

They struggled for land, water and other resources and had to fight with local communities, tribes and sometimes other Hakka.

They had to continuously move until their current settlement - areas full of mountains and forests and a place where historically few others lived. "Combining residence and military defence was a priority for them," said Fang Yong, an architectural professor at Peking University.

Zhencheng Building was the largest remaining circular tulou in Yongding. Its area is 5,000 square metres, like a giant tiger curled up in a narrow valley.

Most of the 8,000 tulou in Yongding are square with only 360 being circular because the latter is more difficult to build.

The building has four floors and 200 rooms. All rooms use the thick circular wall as their back wall and open their doors to the courtyard within the wall.

There is no window in the thick circular wall for the first two floors, and windows for rooms in the upper two floors are as small, not bigger than a slit from which to fire a weapon.

The design seems to explain how earnestly Hakka people hanker for safety, even at the cost of losing sun light in their homes.

Like most tulou, there is only one gate in the huge Zhencheng Building, equipped with thick wooden door covered with sheet iron. There is a gutter above the door, preventing attacking enemies from using fire to break the door.

The soil-made wall is often as thick as 2 metres. In the yard within the wall, there are wells and depositories for storing grains and dried vegetables, able to sustain the dwellers for a long time when besieged by enemies.

But there is still a major enemy for the soil-walls of a tulou... Water. A good soaking by rain makes the mud easy to smash.

In order to make the soil wall strong enough against floods and rain, Hakkas built it on stone groundwork higher than the tallest flood line. Soil was mingled with glutinous rice and sugar soup before it was made into adobes used to build walls. Large eaves were installed to cover the wall from rain drops as much as possible.

There are numerous legends describing how Hakka communities defended themselves against attacking enemies. It was said that one family used to defend themselves for more than one year against a peasant army in late Qing Dynasty (1644-1911).

Another factor promoting Hakka people to build a tulou is their strong awareness of clanship, transcended from ancient Central China.

"The continuous fights and hard natural environment made our Hakka ancestors aware that only family members are reliable, and above all the things, family members had to unite together," said Lin, adding kinship among a Hakka family remains strong.

Three brothers

Zhencheng Building was finished in 1912, but its construction was launched five years earlier.

Its constructors are three brothers in late Qing Dynasty. The three - Lin Deshan, Lin Zhongshan and Lin Renshan - were born in poverty but later became rich by becoming tobacco farmers.

When they became rich, they first of all thought of building a big tulou for the whole Lin clan.

It was not an easy thing at that time because of continuous wars and robberies. The first two brothers died before the building was finished. The youngest one - Lin Renshan - managed to launch the construction but soon died of illness. Meanwhile, their business declined. In order to fulfill his father's will, Lin Hongchao visited all the family members and persuaded them one by one to fund the project.

Lin also visited big cities to absorb ideas and inspiration to build the new tulou. With five years of ceaseless effort, Zhencheng Building was eventually finished.

Lin Hongchao himself also became famous by his firm will to build the soil building, and was elected an congressman of the then young Republic of China. Li Yuanhong, then the president, wrote a tablet for Zhencheng Building.

On the gate of Zhencheng Building, a couplet writes: "Erecting order and principle; being virtuous and talented."

"It is a firm belief among Hakka people that personal moral status is closely connected with the prosperity of the country," Lin Xiaohong said.

Entering Zhencheng Building, couplets and handwriting are everywhere, most describing the importance of being moral, industrious and diligent in learning.

Despite their merchant origin, the Lin clan stressed the importance of a traditional education. Although the budget for constructing their home was tight, the Lin brothers invested well and build several schools for villages in the area.

The biggest rooms of a tulou were reserved for teachers.

"Education is the primary tool to unite the whole clan together when they might have quarreled with each other due to the common residence," Lin said.

Within the big Lin clan, every small family was allotted a group of rooms vertically lined from the ground floor to the fourth floor. The first two floors were used to store food or production tools while the room in the fourth floor was for guests.

In the courtyard within the outside wall, were public bathroom, kitchen and wells, each divided by four to five subfamilies.

All rooms are built with wooden frames and divided with wood blocks. But every four or five rooms are divided with bricks, able to prevent the spread of fire in time of emergency.

In the courtyard, there are some marble sculptures, showing a trend of merging Western culture.

However, in most periods of their history, Hakka people refused the culture and techniques developed by their local neighbours.

Hakka people thought themselves to be culturally superior to other communities. Besides the safety consideration, their tulou was built to maintain their own culture and way of life, keeping their own unique dialect, custom and cuisine behind walls, and protecting their children from the influence of local communities, Fang added.

In the long history of Hakkas' tulou, compact earth and wood were dominant construction material.

By comparison, influenced by Hakka people, Minnan people, mainly living in Xiamen, Quanzhou and Zhangzhou in southern parts of Fujian, began to construct castle-like stone wall building several hundred years ago. The more solid buildings required advanced techniques and tools, and Minnan people often hired Hakkas as designers or engineers.

The Minnan, another branch of ancient Han ethnic group migrating to their current residence in the late Tang Dynasty (AD 618-907), have absorbed local communities and even Arab merchants. They have been famous for migrating to other countries and most people in Taiwan as well as in Singapore can trace their origins to Minnan.

It was discovered by historians that Hakkas tried to move to coastal Minnan areas several times due to their poor living condition in the mountainous areas, but all of these attempts failed because of the strong resistance.

Under threat?

Although nearly all tulous are still dwelled in by people in Hongkeng Village, most of the rooms are empty. A tulou resident told China Daily that many young people went to cities as migrant workers.

Neighbouring each tulou, some modern houses have been built. Lin Xiaohong admitted that many families living within one tulou often make life too noisy.

More importantly, no one is able to coordinate the conflicts between different families within a clan, said Chang Ding, a restaurant owner nearby Zhencheng Building.

"In the past, there were a 'Shaikh' and several senior old men acting as judges within a clan, but now there is no Shaikh or chiefs any more," Chang said.

Lacking daily maintenance, many tulou have become dilapidated in the past 30 years.There has also been a strong trend for Hakkas to migrate worldwide together. In 1971, the first World Conference of Hakkas was held in Hong Kong, and now 19 sessions of the event have been held, each attracting thousands of attendants.

"The tulou might be withering, but not the Hakka culture, never," said Jian Xiaojun, a Hakka and president of Yongding Association of Science and Technology.

(China Daily 11/20/2004 page9)