The Forbidden City is built on three floors. Why? What does this mean?

On July 2 1 day, Beijing was hit by the biggest rainstorm since meteorological records, and serious water accumulated in the city. Some media have a whim: Why didn't the Forbidden City built 600 years ago accumulate water? Is ancient architecture better than modern urban architecture?

In fact, there was water in the Forbidden City that day, but it did not pose a threat to the palace. Since Shang Dynasty, royal palaces have been built on high platforms. Take the Hall of Supreme Harmony as an example. * * * The total height of the three-storey platform is as high as 8.13m. At this height, the possibility of water inflow is negligible.

But it also brings two problems: first, the construction cost is extremely high and the investment efficiency is too low to be truly popularized; Second, it is inconvenient to use. It was really hard for an elderly person to climb such a high staircase in the temple last time. In addition, the stone steps are slippery in winter, which is easy to hurt people. There is a record in history that a minister fell to his death in the early morning.

The Forbidden City is not easy to accumulate water, which is related to the large use of blue bricks. This kind of brick has good water permeability, which can harden pavement and reduce dust, but it is not a perfect solution. After snow water seeps into blue bricks in winter, it will freeze when the temperature drops at night. Ice is bigger than water, and it will squeeze the blue bricks from the inside to make them brittle. It won't be long before the originally flat ground becomes pitted and full of broken bricks, so it can only be re-paved, which is expensive.

Of course, the Forbidden City did pay more attention to waterproofing when it was designed, because Beijing was hit by heavy rains many times in history, so some comprehensive management schemes were adopted in the Ming and Qing Dynasties.

First of all, lakes such as Shichahai in the urban area are protected, and private occupation is strictly prohibited to ensure their water storage capacity. In addition, the wide moat can also play the role of flood diversion. This lightened the pressure of rainstorm and flood on the Forbidden City.

Secondly, the interior of the Forbidden City is high in the middle, low in the side, high in the north and low in the south, and the buildings are at the highest point of the terrain (the so-called "bear back"), so that the water is guided into the ditch by its own weight and discharged into the Neijinshui River, which is more than 2,000 meters long and traverses the whole Forbidden City. It not only beautifies the environment, but also plays a role in drainage and provides fire water.

Third, develop drainage ditches. There are four north-south main canals in the Forbidden City area. The extended drainage ditch covers the Forbidden City and all the surrounding courtyards, forming a complete drainage system. These ditches are all made of stone and can be used as new.

Apart from design factors, not many people lived in the Forbidden City in Ming and Qing Dynasties, especially in Qing Dynasty, because the Qing Dynasty learned the lesson of the Ming Dynasty's national subjugation and deliberately controlled the number of eunuchs. In most periods, the total number of people was only about 3,000, and many of them did not work in the Forbidden City. Moreover, the emperors of the Qing Dynasty did not like the depressing and solemn architectural pattern of the Forbidden City. Kangxi and Qianlong worked in Yuanmingyuan for a long time, and Cixi also stayed in the Summer Palace in her later period. There are few people in the Forbidden City, the service life of the equipment is prolonged, and the drainage pipeline is not easily blocked.

Although the Forbidden City survived storm after storm, old Beijing was not so lucky because of lack of investment and poor management. By the middle and late Qing Dynasty, the function of urban drainage ditch was generally degraded, and once heavy rain occurred, it often caused dramatic disasters. After all, the drainage scheme of the Forbidden City is too expensive to benefit more people.