Maiden's Tower has stood watch on its speck of rock for some 2,400 years — the story begins with an Athenian general who, ancient accounts say, raised a customs post here to tax ships slipping through the strait. The islet kept changing jobs: a Byzantine watch-fort said to anchor a chain across the water, a lighthouse, a quarantine station, a signal post. The trim white tower you see today, with its lead cone, is largely the Ottoman rebuild of 1832 under Mahmud II. Two legends cling to it. In one, an emperor hid his daughter on this rock to escape a prophecy that a snake would kill her. In the other, this is the tower where the Greek swimmer Leander drowned crossing to his lover Hero, though that story really belongs to the Dardanelles, far to the southwest.
The crossing is half the pleasure — a short boat hop from the Üsküdar shore, gulls overhead, the city swinging into view on both continents. On the islet there is barely room to circle the base before the water starts again. Climb to the terrace and Istanbul lays itself out: minarets, the strait's restless ship traffic, the open Marmara to the south. Restored top to bottom in the early 2020s, the tower now holds a small museum and café, and after dark it glows like a lantern set on the water.