Chang’an, the capital city of the Tang Dynasty (618-907 AD), is a world-famous ancient capital and has exerted a profound influence on the planning of capitals in subsequent dynasties.  Extensive research has been conducted on its urban scale, spatial layout, and palace architecture, etc., depicting the majestic and orderly image of the city within its city walls.  However, it is noteworthy that in Tang Dynasty documents, such aas Tang Liu Dian 唐六典 (the Six Statues of the Tang Dynasty), Chang’an was not merely the capital city enclosed by four walls.  Instead, it extended west to the Longshan Mountains and east to the Yellow River, encompassing the core region of today’s Guanzhong Plain, spanning over 400 kilometers.  How should we understand such a “capital city” of immense scale? How was it construstred, and what connection did it have with the natural topography of the Guangzhong Plain?  And what significance does it hold for urban development today?  This lecture will adopt the “triple evidence method”—integrating historical documents, archaeological evidence, and field surveys—to explore possible answers to these questions.