If you arrive in İstanbul by train from Europe, or if you ride in from the airport along the seashore, you will probably notice this fortress looming over the city's southern approaches. One of İstanbul’s major landmarks, it has a history as substantial as its massive structure – starting in 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.

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 now on display in Topkapı Palace’s costumes collection.

The spectacular views from the battlements are the highlight of a visit here, though a lack of handrails or barriers on the steep stone staircases can be offputting for some visitors. Buses 80 and 80T come here from Eminönü and Taksim repsectively. While you’re in the neighbourhood, consider a trip to İstanbul’s best kebapçı, Develi, 2km northeast (towards Sultanahmet) on the same bus lines. You can also walk along the historic land walls all the way to the Golden Horn from here.