Tending her garden, a woman coaxes chard to life outside the ancient Theodosian walls that line the oldest section of the city. Built in the 5th century, four miles of this protective wall still stand—fully intact in some places, fragmented in others—a reminder of Istanbul’s long history. Founded by the Greeks as Byzantium around 660 B.C., transformed into Constantinople by the Romans in A.D. 330, and officially named Istanbul in 1930, the city keeps proving itself a master of reinvention.