Byzantine Wall Ruins

These low masonry remnants in Istanbul's Kumkapı district are what survives of the Julianus Harbor, an artificial port basin constructed in the 4th century AD and known in historical sources as Portus Novus. Built near the Church of Saints Sergius and Bacchus — now the Küçük Ayasofya Mosque — the harbor once served as a major maritime gateway to the Roman and later Byzantine capital. Today four short sections of late-antique rubble masonry survive above ground, grass-covered and unfenced. The site functions as an active car park, with no interpretive signage, making it one of Istanbul's more quietly startling contrasts: a harbor that shaped the medieval Mediterranean, now ignored in plain sight.