It's Istanbul, not Constantinople, that straddles the Bosporus Strait today. But more than half a millennium ago—on May 29, 1453—it was Constantinople, then the last bastion of the Roman Empire, that fell to Ottoman Turks.

It was also in its incarnation as Constantinople that the city was declared the capital of the Roman Empire by Emperor Constantine in 330 A.D. Before that, the site was a Greek village called Byzantine.

The new capital had much to recommend it. It was easier to defend than Rome since it jutted out on the water, it had seven hills just like Rome—and it had a Christian population, the preference of the Emperor.

The strait's Golden Horn, seen here, divides the city in two. The