These pictures are only a few, they show the Marble Tower, which is situated near the Yedikule Fortress, at a point where the sea-walls along the Marmara joined the landwalls. So this is not the Yedikule fortress itself. For years these pictures have had that name, becuse they were poart of one "walk", the way I used to organise my pictures when I had only a few.

The tower is 13 meters square at its base and 30 meters high, its lower half is faced in marble. It is unlike any other structure in the whole defence-system and may have been part of an imperial sea-pavilion. Ruins beside it seem to indicate it was part of a small castle. Beyond the tower there are the sunken remains of a mole which must have been part of the castle harbour. Info from Strolling through Istanbul, guidebook.