Not a city but a world: fifteen continuous centuries as capital of two empires, split by seas and stitched by ferries. Sultanahmet for the two-day history core, Istiklal for modern life, the Bosphorus cruise as obligation not option, and a Kadıköy ferry crossing for the local-eyes Istanbul. Stay Sultanahmet (first trip) or Bosphorus-side; trams and ferries beat the legendary traffic.