One of İstanbul’s historic landmarks, this fortress has a history as substantial as its massive but now sadly dilapidated structure. It dates from the late 4th century, when Theodosius the Great built a triumphal arch here. When the next Theodosius built his massive land walls, he incorporated the arch into the structure. Whilst its history is fascinating, it's not worth making a dedicated trip to visit as the fortress is closed to the public and the surrounding area isn't particularly pleasant.
Under the Byzantines, the great arch became known as the Porta Aurea (Golden Gate) and was used for triumphal state processions into and out of the city. For a time its gates were indeed plated with gold; the doorway was eventually sealed in the late Byzantine period. Four of the fortress’ seven towers were built as part of Theodosius II’s walls; the other three, which are inside the walls, were added by Mehmet the Conqueror.
In Ottoman times the fortress was used for defence, as a repository for the Imperial Treasury, as a prison and as a place of execution. In times of war, ambassadors of ‘enemy’ countries to the Sublime Porte (the Ottoman prime ministery) often ended up incarcerated here. Latin and German inscriptions still visible in the Ambassadors’ Tower bring the place’s eerie history to light. It was also here that Sultan Osman II, a 17-year-old youth, was executed in 1622 during a revolt of the janissary corps. The kaftan he was wearing when he was murdered is part of the Topkapı Palace costume collection.