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In page National and regional identity in Spain:

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Mainland Spain has been characterised historically by relative inaccessibility from outside and by difficult communication between different parts of it. "[W]alls and battlements divide within itself the territory which walls and battlements separate from other countries".[1] In contrast to the "vast monotony" of the central plateau, the surrounding peripheral areas "present to the traveler every possible landscape".[2] Diversity in forms of agriculture and its productivity are conditioned by the contrasts in rainfall between "wet" and "dry" Spain, and to the extent that irrigation has been introduced.[3] In the past the peripheral regions benefited from cheap coastal transport, whereas transport costs and distance hindered the development of the central regions.[4]