Yoros Castle (Anadolu Kavağı)

Yoros Kalesi sits on a wooded hill at the northern end of the Bosphorus, right where the strait opens into the Black Sea. The fortress was built by the Byzantines in the 13th century as part of a defensive chain with the Rumeli Kavağı fortress across the water, then leased to the Genoese in the 14th century as a trading post. It changed hands several times before the Ottomans took it in 1391, and was finally abandoned after a 1509 earthquake.

Today the castle is a romantic ruin — broken stone walls, a roofless inner tower, and a few remaining gun positions, all framed by thick forest. From the top of the walls you can see the Bosphorus stretching south, the Black Sea opening north, and the green hills of the Asian shore falling away on both sides. It's the most-photographed spot in upper Bosphorus and one of the quietest major sites in Istanbul.

Getting there is half the experience: take the Şehir Hatları Bosphorus line ferry from Eminönü (or join it at Beşiktaş) — the boat threads past all the waterfront palaces, under both Bosphorus bridges, and into the forested upper strait. The ferry ride itself is two hours each way. At Anadolu Kavağı, the castle is a 20-minute walk uphill from the pier (or a short dolmuş ride).