Istanbul

For more than two millennia Istanbul has stood at the crossroads of the world, perched at the very tip of Europe, gazing across the shores of Asia. The history of this city--known as Byzantium, then Constantinople, now Istanbul--is at once glorious, outsized, and astounding. Founded by the Greeks, its location blessed it as a center for trade but also made it a target of every empire in history, from Alexander the Great and his Macedonian Empire to the Romans and later the Ottomans. At its most spectacular Emperor Constantine I re-founded the city as New Rome, the capital of the eastern Roman empire, and dramatically expanded the city, filling it with artistic treasures, and adorning the streets with opulent palaces. Around it all Constantine built new walls, truly impregnable, that preserved power, wealth, and withstood any aggressor--walls that still stand for tourists to visit.