Cankurtaran: the Marmara sea walls and the lighthouse
The sea-walls counterpart to Yedikule — Byzantine sea defences, a working lighthouse, Hagia Sophia from below. This is a Claude-drafted route awaiting the editor's walk.

1. Cankurtaran Marmaray
The Marmaray station three minutes from the seafront — between Sirkeci and Yedikule on the line that crosses under the Bosphorus. Walk south out of the station; the sea is right there, and the lighthouse is the first marker.

2. The Byzantine sea walls
A fragmentary stretch of the original Marmara fortification — same Theodosian period as the land walls at Yedikule, the southern half of the same defensive ring. Less continuous than the land walls; what survives is in patches, mostly absorbed into later building.

3. Ahırkapı Feneri
A working lighthouse on the seaward corner of the old city, where the Marmara meets the Bosphorus. The current structure is 19th-c, the function ancient. Topkapı's outer foundations rise above it on the north side.

4. Kennedy Caddesi sahil
The coast road named for John F. Kennedy after 1963. Runs from Sarayburnu west toward Yedikule — modern asphalt over the ancient perimeter. Cars are the main feature; the walking is along the seaward edge, with the train line in between.

5. The climb up to Sultanahmet
Cut north up Kabasakal or one of the stepped lanes that rise from the seafront. The south facade of Hagia Sophia reveals itself as you climb — mass first, decoration second, the way the building was meant to be approached. Most visitors arrive from the west and miss this side entirely.

6. Sultanahmet tram (T1)
Two minutes from the dome. Onto the T1 for Eminönü and Kabataş east, or for Aksaray and the Yedikule land-walls walk west — the same defensive perimeter, the other half.

Cankurtaran: the Marmara sea walls and the lighthouse