Constantinople was built on a promontory with the Marmara on one side, the Golden Horn on the other and the Bosphorus at its head, and the city's religious life was oriented to the water accordingly. Its sea walls ran for kilometres along the Marmara shore; its most venerated relic of the Virgin was kept at Blachernae by the Horn, and the tradition that her robe or her intercession turned back besieging fleets is recorded for more than one siege, giving the Akathist hymn its association with deliverance from the sea.
The Princes' Islands, a small archipelago an hour offshore, held a dense concentration of monasteries and became the empire's standard place of honourable disappearance. Deposed emperors, blinded rivals, empresses removed from power and patriarchs who had lost an argument were tonsured and confined there, and Leslie Brubaker and John Haldon's account of the iconoclast period records both iconophile and iconoclast losers being sent across the same water in turn. Exile to a monastery on these islands was a political sentence expressed in religious form.
The sea was also the approach for the fleets. Arab, Rus, Venetian and Ottoman ships all appeared on it, and the crusader fleet of 1204 crossed it before turning into the Horn to take the city, an event whose consequences for the relation between the eastern and western churches have never been undone.