For a few precious frost-nipped weeks, these museum-piece cities of Olde World Europe flicker back to the Middle Ages -- not the ossified medieval throwbacks of soot-blackened cathedrals and tourist-bedeviled museums, but the living, breathing yesteryear of a bustling outdoor marketplace.

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Created by A-lister Kasper Holten, the Dane known for his Copenhagen Ring cycle and now director of opera of London's Royal Opera House, this "Lohengrin, " which is set in the Middle Ages, actually has principals dressed in medieval-looking costumes.

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They are essential for the study of medieval attitudes towards piety, and the spiritual needs and wellbeing of an urban population in the middle ages.

UNESCO: 2011 UK Memory of the World Register