English: The structure to the right is the Marble Tower, the southernmost tower of the old walls. The walls to the left connect (after a break) to the Yedikule fortress. 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.