Ancient tradition credits the Megarian colonist Byzas with founding Byzantium around this era, choosing a peninsula commanding the strait between Europe and Asia. The site's natural harbor, the Golden Horn, and control over trade routes between the Black Sea and Mediterranean made it strategically priceless. Centuries later Constantine the Great would refound it as his imperial capital, and it would rule as Constantinople for over a thousand years.
The story, preserved mainly through later Greek historians, holds that Byzas consulted the Delphic Oracle before setting sail, and was told to found his city 'opposite the land of the blind.' Arriving at the mouth of the Bosphorus, he supposedly noticed that fishermen across the strait in Chalcedon had failed to spot the obvious advantages of the opposite shore, its defensible peninsula, freshwater streams, and the deep natural harbor now known as the Golden Horn, so he judged them figuratively blind and settled there instead.
Whatever the truth of the legend, the location proved to be one of the most consequential real-estate choices in history. Whoever held this narrow crossing between Europe and Asia could tax and control trade between the Aegean and the Black Sea, and could also dominate any land army trying to march between the two continents.
Byzantium remained a modest Greek trading city for centuries, drawn into Persian, Athenian, and Spartan spheres in turn, until Emperor Constantine recognized the same strategic genius that Byzas supposedly had, and rebuilt it in 330 AD as Constantinople, the new capital of the Roman Empire.