Why did the Hakka people in Fujian create this characteristic building, the Big Picture Building?

Tulou * * * is characterized by a long construction period, which generally takes two or three years to complete, and the older one even needs decades and generations of craftsmen's hard work. The wood used must be 300 ~ 500 cubic meters. Because the earth wall is thick under and narrow on the top, it is strong and firm, and its "three defenses" (windproof, waterproof and shockproof) performance is good, and some can also prevent fire (the three-ring earth wall is a wall built by three walls), especially its extraordinary earthquake resistance is amazing. Almost all the earth buildings have been tested by earthquakes to varying degrees and are safe and sound. Tulou, as a proud architectural form of Hakka people in Fujian, is a treasure in Fujian folk houses. At the same time, it also incorporates human factors, which can be called the epitome of the combination of heaven, earth and people. Dozens of families and hundreds of people go to the first floor together, which embodies the family tradition of Hakka people living in harmony. Therefore, a tulou history is a rural family history. Descendants of Tulou often can tell the origin of Kan Kan family without genealogy. In addition, the use of local materials and the most common soil materials to build tall castles, turning ordinary into magic, reflecting the unique creation of Hakka people in the process of conquering nature.