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A defensive wall is a fortification used to protect a city, town or other settlement from potential aggressors. In ancient to modern times, they were used to enclose settlements. Generally, these are referred to as city walls or town walls, although there were also walls, such as the Great Wall of China, Walls of Benin, Hadrian's Wall, and the metaphorical Atlantic Wall, which extended far beyond the borders of a city and were used to enclose regions or mark territorial boundaries. Beyond their defensive utility, many walls also had important symbolic functions – representing the status and independence of the communities they embraced. Existing ancient walls are almost always masonry structures, although brick and timber-built variants are also known. Depending on the topography of the area surrounding the city or the settlement the wall is intended to protect, elements of the terrain (e.g. rivers or coastlines) may be incorporated in order to make the wall more effective. Walls may only be crossed by entering the appropriate city gate and are often supplemented with towers. The practice of building these massive walls, though having its origins in prehistory, was refined during the rise of city-states, and energetic wall-building continued into the medieval period and beyond in certain parts of Europe. Simpler defensive walls of earth or stone, thrown up around hillforts, ringworks, early castles and the like, tend to be referred to as ramparts. == History == From very early history to modern times, walls have been a near necessity for every city. Uruk in ancient Sumer (Mesopotamia) is one of the world's oldest known walled cities. Before that, the city (or rather proto-city) of Jericho in what is now the West Bank had a wall surrounding it as early as the 8th millennium BC. The Assyrians deployed large labour forces to build new palaces, temples and defensive walls.〔Banister Fletcher's A History of Architecture By Banister Fletcher, Sir, Dan Cruickshank, Dan Cruickhank, Sir Banister Fletcher. Published 1996 Architectural Press. Architecture. 1696 pages. ISBN 0-7506-2267-9. pg no 20〕 Some settlements in the Indus Valley Civilization were also fortified. By about 3500 B.C., hundreds of small farming villages dotted the Indus floodplain. Many of these settlements had fortifications and planned streets. The stone and mud brick houses of Kot Diji were clustered behind massive stone flood dykes and defensive walls, for neighboring communities quarreled constantly about the control of prime agricultural land.〔The Encyclopedia of World History: ancient, medieval, and modern, chronologically arranged By Peter N. Stearns, William Leonard Langer. Compiled by William L Langer. Published 2001 Houghton Mifflin Books. History / General History. ISBN 0-395-65237-5. pg 17〕 Mundigak (c. 2500 B.C.) in present-day south-east Afghanistan has defensive walls and square bastions of sun dried bricks.〔Banister Fletcher's A History of Architecture By Banister Fletcher, Sir, Dan Cruickshank, Dan Cruickhank, Sir Banister Fletcher. Published 1996 Architectural Press. Architecture. 1696 pages. ISBN 0-7506-2267-9. pg no 100〕 Babylon was one of the most famous cities of the ancient world, especially as a result of the building program of Nebuchadnezzar, who expanded the walls and built the Ishtar Gate. Exceptions were few — notably, ancient Sparta and ancient Rome did not have walls for a long time, choosing to rely on their militaries for defense instead. Initially, these fortifications were simple constructions of wood and earth, which were later replaced by mixed constructions of stones piled on top of each other without mortar. In Central Europe, the Celts built large fortified settlements which the Romans called oppida, whose walls seem partially influenced by those built in the Mediterranean. The fortifications were continuously expanded and improved. In ancient Greece, large stone walls had been built in Mycenaean Greece, such as the ancient site of Mycenae (famous for the huge stone blocks of its 'cyclopean' walls). In classical era Greece, the city of Athens built a long set of parallel stone walls called the Long Walls that reached their guarded seaport at Piraeus. Large tempered earth (i.e. rammed earth) walls were built in ancient China since the Shang Dynasty (c. 1600-1050 BC), as the capital at ancient Ao had enormous walls built in this fashion (see siege for more info). Although stone walls were built in China during the Warring States (481-221 BC), mass conversion to stone architecture did not begin in earnest until the Tang Dynasty (618-907 AD). In terms of China's longest and most impressive fortification, the Great Wall sections had been built prior to the Qin Dynasty (221-207 BC) and subsequently connected and fortified during the Qin dynasty, although its present form was mostly an engineering feat and remodeling of the Ming Dynasty (1368–1644 AD) during the 15th and 16th centuries. The large walls of Pingyao serve as one example. Likewise, the famous walls of the Forbidden City in Beijing were established in the early 15th century by the Yongle Emperor. The Romans fortified their cities with massive, mortar-bound stone walls. The most famous of these are the largely extant Aurelian Walls of Rome and the Theodosian Walls of Constantinople, together with partial remains elsewhere. These are mostly city gates, like the Porta Nigra in Trier or Newport Arch in Lincoln. Apart from these, the early Middle Ages also saw the creation of some towns built around castles. These cities were only rarely protected by simple stone walls and more usually by a combination of both walls and ditches. From the 12th century AD hundreds of settlements of all sizes were founded all across Europe, who very often obtained the right of fortification soon afterwards. The founding of urban centers was an important means of territorial expansion and many cities, especially in central and eastern Europe, were founded precisely for this purpose during the period of Eastern settlement. These cities are easy to recognise due to their regular layout and large market spaces. The fortifications of these settlements were continuously improved to reflect the current level of military development. During the Renaissance era, the Venetians raised great walls around cities threatened by the Ottoman Empire. Among the finest examples are the walled cities of Nicosia and Famagusta in Cyprus and the fortifications of Candia and Chania in Crete, which still stand to this day. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Defensive wall」の詳細全文を読む スポンサード リンク
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