Beijing is an ancient city with a history of nearly 3,000 years. This ancient city has spread many stories and legends that are either sad or graceful, cool, shocking, happy or joyful. Most of the people who created these have turned into wisps of loess and become witnesses of the city of Beijing from thousands of years ago to the present. But such a great city was destroyed by a little girl's smile... Is this a classic case of the macroscopic manifestation of the butterfly effect?