The towers and ramparts surround Istanbul from southwest is called Yedikule Castle or Yedikule Dungeons. Theodosius I had made a triumphal arch, this arch had been the entrance door of the city in 412, Theodosius II had added two towers at left and right sides of the arch. Generally emperors coming from a triumph passed through the door that led to the biggest street of the city. The front and belt of the door are gilded; hence the door is called as “Yaldizli Door” (Gilded Door). Kantakuzenos IV added one more tower near each of the tower. In the 15th century the height of the middle fairway was reduced to 4 m to 8 m and this fairway was closed. After the conquest of Istanbul, Mehmed the Conqueror had three towers in different heights built and bended them to other towers and ramparts in 1470. With these towers the Yedikule is turned out to be castle.
The Byzantines used one of the towers as a dungeon and the executions were made here, torture equipments, prison cells and wells are still remaining.
The Ottomans used this tower as a prison too. In the marble tower on the left of the main door there is a deep well named as “Kanlikuyu” (Bloody well). The criminals were executed near this well and their heads were thrown into the well. At the bottom of the well, there is channel that opens to Marmara Sea. The thrown heads were dragged to the sea by the help of the sea hitting to the bottom of the well. In the middle flat of this tower there are two rooms, one of them is small and lack of window, the other is big. A lot of political guilty people were imprisoned there, and Sultan Othman II was killed in Yedikule. It is used as a museum today.