The earthen houses of Yongding，Fujian，found inthe southern part of the Longyan region，have avery long history.They are unique in character，they are also very large in scale and well crafted.Thisstyle of building has been called“a skill unique to China.”
Yongding earthen houses are found in two types，square and round.There are 360 round buildings andover 4，000 square ones in Yongding County，Fujian.Theround buildings，also known as round stockaded villages，are typical among Hakka residents，and usually consist of two to three concentric circles.The outer circle is usuallythree or four stories tall，contains 100–200 rooms andis over ten meters in height.The first floor is the cookingand dining area，the second floor is for storage and thethird and fourth for the bedrooms.The two-story secondcircle contains 30–50 rooms，usually used for guestrooms.In between is the ancestral hall，a common areaused by the several hundred residents for marriages，funerals，and parties.Also included in the compounds arewater wells，public baths，and flour mills.The buildingsare made from tamped earth obtained locally and do notrequire reinforced concrete.The walls are 3 meters thickat the base，wide enough to drive a car on，and the lowerlevel walls are 1.5 meters thick，wide enough that a personcould lie across it.The wall narrows from bottom totop，but it is usually at least 0.9 meters thick at the top.
Wooden planks are used following the inside curve of thewalls to form a great number of rooms，and the inner sideof the planks form a corridor.
The earthen houses of Yongding，Fujian were mostlybuilt during the Ming（1368–1644）and Qing dynasties（1644–1911），but their origin goes all the way back to theWestern Jin Dynasty（265–316）。About that time the Hakkapeople moved into the area to escape poor agriculturalconditions and transformed simple mud brick dwellingsinto strong and beautiful earthen homes，gradually addingmore stories to the structure.Beginning in the middleof the Ming Dynasty，the houses were built bigger andbigger in scale.This kind of structure can not only resistnatural disasters such as typhoons and earthquakes，butmanmade disasters such as bandit raids as well.Moreover，it allowed the dispersed Hakka people to live togetherin one place.The people spent most of their daystogether and got along well，so when threatened by anemergency from the outside they united as one to face thethreat.
From ancient times to the 1940s，the earthen housesserved as a sturdy bunker for the self-protection of theHakka people.The main gate of the compound is 20–30cm thick and made of trees with no commercial valueplated with iron on the outside and some even have waterchannels for fire protection above them.The first andsecond floors of round houses have no windows to pre-vent enemies from entering.The corridor between the innerand outer walls is sometimes as narrow as one meterwide and runs all the way around the wall.The windowson the outside wall not only provide ventilation and naturallight，but also make it convenient to combat outsideenemies and protect themselves.Some earthen houseshave lookout platforms at the front and two sides of thehighest points so they could maintain a lookout for anytrouble coming in the distance.In addition to being goodfor protection and keeping out enemies，the Yongdingearthen houses resist earthquakes and fires，keep out wildanimals，and allow good ventilation and natural lighting.
For good fire protection，the outer walls of some earthenhouses are divided into 6，8，or 10 sections separated byfirewalls to prevent a fire from spreading to the wholevillage.Since the rooms are distributed along the curveof the wall in round houses，there are no dead corners asthere are in conventional apartment buildings，makingthem superior in terms of light and ventilation.The thickwalls provide good insulation，so the inside of the rooms iswarm in the winter and cool in the summer.
The Zhencheng building，located in Hongkeng Villageof Hukeng Township，was built in 1912 and covers anarea of 5，000 square meters.It is perched on mountainlikebeams and consists of two concentric circles.Theouter circle is four stories tall with 48 rooms in each storyarranged according to the Eight Trigrams of the Yi Ching.
Each section contains 6 rooms and has its own stairway.
The ancestral hall of the Zhencheng building is in theform of a stage in front of which stands four stone pillarseach nearly 2 meters in circumference and nearly 7 metersin height.The cast iron lattice guardrail on the secondfloor walkway was shipped to Hukeng Village fromShanghai.Over the door to the main hall are the wordsof an early Nationalist president，Li Yuanhong（1864–1928）。The Zhencheng building was displayed along withthe Yonghegong Lamasery and Great Wall at the World’sFair of Architectural Models held in Los Angeles in April1986.