Alhambra, Spain

Built by the Moorish rulers of Granada between 1238 and 1358, the Alhambra is Europe's finest example of Islamic architecture and one of the best-preserved medieval palace complexes in the world. Its intricate stucco carvings, geometric tile work, and garden courtyard fountains were described by the 19th-century writer Washington Irving as "a dream in marble." It is Spain's most visited monument, drawing 2.7 million visitors annually, with tickets selling out months in advance.