The Great Wall of China is a series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China to protect the Chinese states and empires against the raids and invasions of the various nomadic groups of the Eurasian Steppe. Several walls were being built as early as the 7th centuryBCE; these, later joined together and made bigger and stronger, are now collectively referred to as the Great Wall. Especially famous is the wall built 220–206BCE by Qin Shi Huang, the first Emperor of China. Little of that wall remains. Since then, the Great Wall has on and off been rebuilt, maintained, and enhanced; the majority of the existing wall is from the Ming Dynasty.
Other purposes of the Great Wall have included border controls, allowing the imposition of duties on goods transported along the Silk Road, regulation or encouragement of trade and the control of immigration and emigration. Furthermore, the defensive characteristics of the Great Wall were enhanced by the construction of watch towers, troop barracks, garrison stations, signaling capabilities through the means of smoke or fire, and the fact that the path of the Great Wall also served as a transportation corridor.
In physical cosmology, galaxy filaments (subtypes: supercluster complexes, galaxy walls, and galaxy sheets) are the largest known structures in the universe. They are massive, thread-like formations, with a typical length of 50 to 80 megaparsecs h−1, (163 to 261 million light years) that form the boundaries between large voids in the universe. Filaments consist of gravitationally bound galaxies; parts where a large number of galaxies are very close to each other (in cosmic terms) are called superclusters.
In the standard model of the evolution of the universe, galactic filaments form along and follow web-like strings of dark matter. It is thought that this dark matter dictates the structure of the Universe on the grandest of scales. Dark matter gravitationally attracts baryonic matter, and it is this "normal" matter that astronomers see forming long, thin walls of super-galactic clusters.
China has long been a cradle and host to a variety of the most enduring religio-philosophical traditions of the world. Confucianism and Taoism, plus Buddhism, constitute the "three teachings", philosophical frameworks which historically have had a significant role in shaping Chinese culture. Elements of these three belief systems are incorporated into folk or popular religions. Chinese religions are family-oriented and do not demand exclusive adherence, allowing the practice or belief of several at the same time. Some scholars prefer not to use the term "religion" in reference to belief systems in China, and suggest "cultural practices", "thought systems" or "philosophies" as more appropriate terms. The emperors of China claimed the Mandate of Heaven and participated in Chinese religious practices. Since 1949, China has been governed by the Communist Party of China, which, in theory, is an atheist institution and prohibits party members from belonging to a religion. During Mao Zedong's rule, religious movements were oppressed. Under following leaders, religious organisations have been given more autonomy. At the same time, China is considered a nation with a long history of humanist and secularist, this-worldly thought since the time of Confucius, who stressed shisu (Chinese:世俗; pinyin:shìsú, "being in the world"), and Hu Shih stated in the 1920s that "China is a country without religion and the Chinese are a people who are not bound by religious superstitions". The Party formally and institutionally recognises five religions in China: Buddhism, Taoism, Islam, Protestantism, and Catholicism (though despite historic links, the Party enforces a separation of the Chinese Catholic Church from the Roman Catholic Church), and there has been more institutional recognition for Confucianism and the Chinese folk religion.