Introduction to the changes in the five capitals of Yan State: The whereabouts of the capitals of Yan State after the mid-10th century BC have not been traced so far. However, since the mid-eighth century, documents and some archaeological discoveries show that the capital of Yan State has undergone many changes. It was not until the end of the third century BC that history finally selected a permanent geographical coordinate for its hub city at the northernmost tip of the North China Plain. ——The geographical coordinates of Beijing today.