Istanbul makes an excellent base for excursions. The Princes' Islands (Adalar) are a 45-minute ferry ride in the Sea of Marmara — car-free, pine-forested, and a complete change of pace from the city. The full Bosphorus ferry to Anadolu Kavağı at the mouth of the Black Sea is another classic, passing fortresses, Ottoman yalıs, and fishing villages. For longer trips, Bursa (Ottoman imperial capital, 2 hours by fast ferry and bus) and the ancient ruins at Troy or the thermal pools at Pamukkale are both doable in a long day.