What to see in Istanbul on a second 4-day trip after visiting the main sights?

In late September–early October Istanbul hosts several overlapping cultural events worth adding to a repeat visit: European Heritage Days from September 12 to 21, the Contemporary Istanbul exhibition at Tersane Istanbul from September 24 to 27, the 'Türkiye Kültür Yolu' festival with concerts and exhibitions from September 26 to October 4, and the international 212 Photography festival from September 26 to October 11, during which the whole city becomes an open-air gallery with dozens of exhibitions and screenings from artists worldwide.

Another reason for a repeat visit: on September 26 the historic Haydarpaşa train station in the Kadıköy district on the Asian side reopens after restoration, and it can be included in a walk around that neighborhood.

On the Asian side, add Üsküdar and the characterful Kuzguncuk neighborhood; Nakkaştepe Park is a good choice for panoramic views and can be combined with both. On the European side, consider a walk around Arnavutköy.

For independent planning, an Istanbul MAPS.ME interactive map lists more than 150 locations, including viewpoints, museums, green corners, cafés, restaurants, and shopping stops. The map costs 599 RUB.

After Hagia Sophia, Topkapı, and Dolmabahçe, focus on less obvious parts of the city: Kadıköy on the Asian side, the characterful Fener and Balat districts, Chora Church, and the Pierre Loti viewpoint.

Set aside one day of a repeat visit for the Princes’ Islands and consider adding the Theodosius Cistern. This makes a good change from the usual Bosphorus cruise, Grand Bazaar, and Galata Tower circuit.