It is in the district it gives its name and Istanbul’s most famous promenade once upon a time where Göksu Stream flows into the Bosphorus. It was built by Bayezid I the Thunderbolt who also aimed to conquer Istanbul like the Conqueror in years between 1394 and 1395.
This first structure consists of a 25 meters high tower with a square plan, and walls surrounding it. Later, Sultan Mehmet the Conqueror strengthened this castle with thicker walls and bastions to strengthen the attack power while building the Rumeli Castle. It is closed to visitors.