Great Wall
The Great Wall was ancient China's integrated defense system, consisting of a series of high and sturdy walls and passes built by exploiting natural geographical features to stop the assaults by enemy cavalry forces. Spanning its length are various fortifications, including passes, military fortresses, cas- tles, garrison stations, and beacon towers, in addition to walls that served as the defense system's backbone. The Great Wall is an engineering marvel in ancient China and in the history of human civilization.
The history of the Great Wall can be traced back to the Western Zhou Dynasty (1046-771 B.C.). By the time of the Spring and Autumn period (770-476 B.C.), various states con- structed extensive fortifications to protect their borders. When China was unified in the Qin Dynasty (221 B.C.-206 B.C.), sections of these earlier fortifications were repaired and linked to form the renowned "10,000-li Long Wall" (2 li approxi- mately equal to 0.6 miles [1 kilometer]). From then on until the Ming (1368-1644) and Qing (1616-1911) dynasties, almost every dynasty took action to restore and rebuild the Great Wall. Over the course of more than 2,000 years, its length totaled more than 21,000 kilometers with over 43,000 historic sites. Such a colossal project is unparalleled in China and the world, earning it a spot among the "Seven Wonders of the Medieval World." Today, the remaining sections of the wall are primarily located in 15 provinces, autonomous regions, and municipalities in northern China; notable sections include the Shanhaiguan Pass in Hebei Province, the Jiayuguan Pass in Gansu Province, and the Badaling and Simatai sections in Beijing.
The Great Wall also has geographical, historical, and cultural significance. It stretches along the 400mm isoline of mean annual precipitation in northern China, serving as a dividing line between agricultural and nomadic civilizations and help- ing maintain peace between the agrarian and nomadic groups and facilitate long-term, large-scale, and continuous exchanges between them. The construction and defense of the Great Wall also promoted the extensive integration of the Han and ethnic minorities in ancient China, making significant contributions to the formation and development of a pluralistic and integrated Chinese nation. A large number of ancient literary masterpieces were based on the theme of the Great Wall, with the frontier poems of the Tang Dynasty (618-907) being the most prominent. These works add cultural meaning to the Great Wall. Over the centuries, the Great Wall has become a symbol of the Chinese nation's wisdom and strength, a testament to the Chinese people's political tradition of great unity. In modern times, it has also come to symbolize the Chinese nation's deter- mination to resist aggression and protect unity. In 1987, it was included on the UNESCO World Cultural Heritage List.
長城
長城是中國古代的軍事防御工程，是依托地形地勢建造的高大、堅固且連綿不斷的長垣與關隘，用以限隔敵方騎兵的行動。長城不單單是一道城墻，而是以城墻為主體，以隘口、軍堡、關城、衛所、烽火臺等多種防御工事連接形成的一套完整的防御體系，是中國古代一項偉大的建筑工程，也是人類文明史上的一大奇跡。
長城的修筑可追溯至西周時期。春秋戰國時期，列國因戰爭防守需要而大量修筑長城。秦代統一中國后，將列國長城進行大規模修繕、連接，筑起了"萬里長城"。此后直至明清時期，歷朝歷代幾乎都有修筑長城的行動。長城的修筑延續2000多年，歷代長城總計長度超過2.1萬千米，各類遺存超過4.3萬處。這樣浩大的工程在中國和世界上都是絕無僅有的，人們因此將長城列為世界中古七大奇跡之一。目前，長城遺存主要分布在北方15個省區市，其代表性地段有山海關（河北）、嘉峪關（甘肅）、八達嶺長城（北京）、司馬臺長城（北京）等。
長城具有豐富的地理、歷史和文化內涵，其走向與中國北方的400毫米等降水量線基本吻合，是農耕文明和游牧文明的分界線，有效維護了二者之間的和平，為兩種文明長時段、大規模、持續交流創造了穩定環境。長城的修建和戍守促進了中國古代漢族與少數民族的廣泛融合，對中華民族多元一體格局的形成和發展作出重要貢獻。以唐代的邊塞詩為代表，古代的文人墨客以長城為題材創作了大量優秀的文藝作品，豐富了長城的文化內涵。長城凝結著中華民族幾千年的智慧與力量，象征著中華民族大一統的政治傳統和民族意志，近代以來更成為中華民族抗擊侵略、維護統一的精神標識。1987年，長城列入聯合國教科文組織世界文化遺產名錄。
