I believe that many people who have been to Beijing will be very interested in Beijing's architecture. Many of them are red bricks and green tiles, which are very beautiful. However, apart from those buildings, many buildings in Beijing, such as the Great Wall and the ancient city walls, are built with blue bricks instead of red bricks. Do you know what's the special significance of this?

First of all, compared with the Great Wall, the well-preserved architectural history we see is relatively short. For example, the red brick we saw in the Forbidden City was actually not the red brick on it, but it was painted with a layer of paint. When you see the Forbidden City, you may think of red bricks and green tiles. But in fact this is only a superficial phenomenon.

Then because a very professional person came out to explain, because the blue bricks should be poured with cold water after they are red, and they can only be used when they are cold. Therefore, the quality of blue bricks will definitely be much better than that of red bricks, which is also the reason why blue bricks are well preserved. Perhaps ancient people used more red bricks, because the quality of red bricks is worse than that of blue bricks, and the technology is relatively simple, so many ordinary people can use this kind of bricks. But because the quality is not very good, it cannot be preserved for thousands of years like blue bricks, and many of them may have disappeared. It's just that we look at a lot of things now and take it for granted that many people in ancient times only used blue bricks instead of red bricks.

Therefore, to sum up, the quality of blue bricks is better than that of red bricks, and they can stay longer.