Beijing is an open and mysterious city, where many secrets happen every day, and we can only see the results. In fact, this is the fun. Every secret has an unknown process. Many people stand up and say that it is so, and more people come to refute or give new explanations. This is the fun. It is best never to know what we don't know. In fact, although we can see the result, we never know the answer. The secret is caught in the passage of time and becomes forever...