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The only country spanning two continents, split by the Bosphorus strait between Europe and Asia. The Hagia Sophia in Istanbul opened as a cathedral in 537 CE, became a mosque in 1453, a museum in 1935, and a mosque again in 2020, nearly 1,500 years of continuous use.

Hagia Sophia, Istanbul
Photo: Arild Vagen, CC BY-SA 3.0