Just like Sultan Mehmed the Conquerer, Sultan Beyazıd I was naturally intent on conquering Istanbul and during the decline of Byzantine Empire, had been keeping a keen eye on the city, for all the great rulers in history. And he had always dreamed of conquering Istanbul.
The fortress was built by Beyazıd I in 1394 with the purpose of controlling the straits leading into the city. However, defeated by Timur in the Battle of Ankara, he never accomplished his aim. It is quite a small fortress, parts of which have been destroyed and parts of which have simply disappeared.
Festival Cannons were shooted from here
Festival cannons were shooted from Anatolia and Rumeli Fortress in the second half of 19th century. When Sultans appeared on Bosphorus, they are saluted with cannon shot which was shooted from fortresses.