Geocaching country souvenir: China
This cache is part of Cache Quest 360, a Worldwide Geocaching Series in almost every country on Earth, promoting the hobby as a worldwide phenomenon.
这个宝藏是Cache Quest 360 的一部分，一个遍布近乎所有国家的全球性Geocaching活动，旨在将这项爱好推广为一个世界级现象。
Another cache of this series in Beijing: Cache Quest 360 - Beijing 北京 (https://coord.info/GCBBJJJ)
Please be stealthy and avoid muggles. After logging, restore the cache as shown in the spoiler —this helps keep it well-protected for future finders and for any trackables inside. Thank you for your cooperation.
请避开路人，签到后按spoiler中的方式复原宝藏，这会有助于宝藏和追踪物们的安全，谢谢配合。
The cache is located at the trailhead of the Mutianyu Great Wall. For more information about the Mutianyu Great Wall, please refer to Warm up cache - Mutianyu.
藏点位于慕田峪长城登山口处，更多有关慕田峪长城的介绍请参考Warm up cache - Mutianyu。
Note:
Maps in mainland China follow the GCJ-02 coordinate system rather than the international WGS-84 system. This results in a 50–500 meter offset in Google Maps or satellite imagery displayed in the official app. Please select OpenStreetMap in the official app, or use the official website, L4C, or a dedicated GPS device.
中国大陆的地图遵循GCJ-02坐标系，而不是国际WGS-84坐标系。这会导致谷歌地图或官方应用程序中的卫星图像产生50-500米的偏移。请在官方app中选择OpenStreetMap, 或使用官网, L4C和专用GPS设备。
The Great Wall of China (万里长城, literally "ten thousand li long wall") is a series of fortifications in China. They were built across the historical northern borders of ancient Chinese states and Imperial China as protection against various nomadic groups from the Eurasian Steppe. The first walls date to the 7th century BC; these were joined together in the Qin dynasty. Successive dynasties expanded the wall system; the best-known sections were built by the Ming dynasty (1368–1644).
To aid in defense, the Great Wall utilized watchtowers, beacon towers, troop barracks, garrison stations, signaling capabilities through the means of smoke or fire, and its status as a transportation corridor. Other purposes of the Great Wall have included border controls (allowing control of immigration and emigration, and the imposition of duties on goods transported along the Silk Road), and the regulation of trade.
The collective fortifications constituting the Great Wall stretch from Liaodong in the east to Lop Lake in the west, and from the present-day Sino–Russian border in the north to Tao River in the south: an arc that roughly delineates the edge of the Mongolian steppe, spanning 21,196.18 km (13,170.70 mi) in total. It is a UNESCO World Heritage Site, and was voted one of the New 7 Wonders of the World in 2007. Today, the defensive system of the Great Wall is recognized as one of the most impressive architectural feats in history.
The construction of the Great Wall followed the fundamental principle of 'building according to the terrain and securing passes by taking advantage of natural defenses.' 'Building according to the terrain' means adapting the engineering work to local topographical conditions and fully utilizing natural resources on site when selecting suitable building materials. 'Securing passes by taking advantage of natural defenses' refers to making use of geographical barriers to fend off enemies. This principle not only enhanced defensive capabilities but also reduced the need for construction materials.
The building of the Great Wall spanned more than two thousand years, from the Spring and Autumn period to the late Ming dynasty. Because productivity and technological levels varied across eras, and because different regimes faced different military circumstances, the construction methods, structural designs, and forms of the Wall differed throughout history. Moreover, due to variations in regional geography, even sections built during the same period could look quite different.
From the perspective of historical periods and the development of fortification techniques, dynasties prior to the Northern Wei mainly built the Wall using tamped-earth rammed construction. Brick-and-stone structures appeared during the Northern Wei. By the Ming dynasty, stone masonry, brick masonry, and mixed brick–stone masonry had become widely used. Cross-sectional observations even reveal applications of trigonometric principles, particularly in reinforcing steep slopes.
Watchtower 敌楼
长城（万里长城，字面意思是“一万里长的墙”）是中国境内的一系列防御工事。它们横跨古代中国诸侯国和帝国时期中国北部边境，用于抵御来自欧亚草原的游牧民族。最早的长城可以追溯到公元前7世纪；秦朝时期，各段长城被连接起来。此后的朝代不断扩建长城；其中最著名的部分是由明朝（1368-1644年）修建的。
为了防御，长城利用了敌楼、烽火台、兵营、驻军站、烟火信号系统以及其作为交通要道的地位。长城的其他用途还包括边境管制（控制人口的出入境，并对丝绸之路上的货物征收关税）和贸易管理。
长城由一系列防御工事组成，东起辽东，西至罗布泊，北起今天的中俄边境，南至沱江，呈弧形，大致勾勒出蒙古草原的边缘，总长21196.18公里（13170.70英里）。它是联合国教科文组织世界遗产，并于2007年被评为世界新七大奇迹之一。如今，长城的防御体系被公认为历史上最令人叹为观止的建筑奇迹之一。
长城的构筑，以“因地形，据险制塞”为基本法则。“因地形”，即指根据地形条件而构筑工程，和充分利用在地的自然资源选择合适的建筑材料。“据险制塞”，主要是指利用地理天险御敌。这条原则有利于防守，也可以节省建筑材料。
Beacon tower 烽火台
长城的修筑从春秋到明后期，持续了两千多年。由于各个时代的生产力、技术水平不同，也由于各个政权所面临的军事形势不同，历代修建的长城在构造、建筑方法及形制方面都互有不同；而由于各处地理条件的差异，即使同一时代所修的长城面貌也有不同。
就不同历史时期和筑城技术的发展而言，北魏以前各朝所修的长城，以版筑夯土为主，北魏时出现了砖石结构的长城，明代长城则广泛运用了石砌法、砖砌法、砖石混砌法，从横切面之观察更含三角学上的应用，特别在陡坡上的巩固方面起了作用。
Old Dragon's Head, part of Shanhai Pass, is where the Great Wall meets the Bohai Sea 山海关老龙头