The Palace Museum is now a famous historical and cultural attraction in China, but some people say that the central axis of the Beijing Palace Museum is not due south but due north, but inclined at a certain angle. In fact, the central axis of Beijing was fixed when the city was built in the Yuan Dynasty, and it has not changed since the Ming and Qing Dynasties. However, an old gentleman named Kun Zhongyu found that the central axis of the Palace Museum seemed a little tilted.

First, Kui Zhongyu found the tilt. Mr. Kui Zhongyu is a rigorous researcher, so he found a map of Beijing, selected several central points located on the central axis of Beijing, the bell tower at the northern end of Yongdingmen Bridge at the southern end and the intersection of Di 'anmen in the middle, and began to measure. The measurement results show that there is an included angle between the meridian and the central axis, which is about 2 degrees 10 minute. Then, China people had clearly measured the meridian at that time. Why did they make such a mistake? Therefore, Zhong Yu Kun studied the history of Beijing.

Second, there has been no change in history. We all know that Beijing was built on the basis of Yan Dadu. These two walls are not due south, but due north. They are parallel to the central axis of Beijing. Therefore, it can be judged that when the Yuan Dynasty established the Yuan Metropolis, the central axis of Beijing deviated from the meridian. In the Ming Dynasty, Judy moved the capital to Beijing in the south of the city, but the direction of the central axis remained unchanged. The central axis of the capital of the Ming Dynasty followed that of the Qing Dynasty and remained unchanged.

Third, the relationship between Yuan Dadu and Yuan Shangdu. When the Yuan Dynasty was founded, Kublai Khan's ministers Liu and Guo Shoujing presided over the construction. They are all from Xingtai, Hebei. Guo Shoujing was a first-class astronomical mathematician and geodetic surveyor at that time, so there would be no such error. So Wei Xiao finally worked out Kublai Khan's birthplace in Yuan Shizu, where Du Yuan is located. He found that when Du Yuan was built, the central axis used the Du Yuan line as the baseline, so there was inclination and deviation. That year, Kublai Khan signed in from Du Yuan. So Kublai Khan's wish is to realize the unification of the two capitals, so he adopted a central axis connecting the two capitals.