Anadolu Kavağı is the last stop on the Bosphorus ferry line, a fishing village a few kilometres short of the Black Sea. The waterfront is lined with seafood tables and the smell of grilling fish. Above it, on the hill, stand the broken walls and twin gate-towers of Yoros Castle. You climb a steep lane past tea gardens to reach them, and from up there the whole geography explains itself: two continents pinching together and tankers threading the current below.
The Byzantines raised the castle to command the strait's narrow neck, and Genoese traders and then Ottoman garrisons held it in turn; its banded stone-and-brick walls still frame the view. For sailors in antiquity this headland was a threshold worth fearing. Before crossing into open water they left offerings at a shrine to Zeus Ourios, the god of fair winds, and the promontory has carried a version of that sacred name ever since: Hieron, then Yoros. On a clear day the horizon from up here is all water and sky.