Nine islands in the Sea of Marmara, 12 km from the Istanbul waterfront, reached by a 45–60 minute ferry from Kabataş or Bostancı. The four largest — Büyükada, Heybeliada, Burgazada, and Kınalıada — are the destinations. No private cars are allowed; transport is by horse-drawn carriage, bicycle, or foot, giving the islands a pace that feels nothing like the city you left an hour ago.
Büyükada is the largest and most visited, with Victorian-era wooden mansions, pine forests, and a monastery at the island's highest point. Heybeliada is smaller, quieter, and has a respected naval academy. Come on a weekday to avoid Istanbul day-trippers. The ferry ride itself — approaching the city from the sea on the return journey, with the Sultanahmet skyline appearing on the horizon — is one of the best views Istanbul offers.