The Anadolu Hisarı (English: Anatolian Fortress) is located in in Beykoz (on the Asian Side), at the narrowest point of the Bosphorous. It was built in 1395 by Beyazit I and is made up of a citadel and its exterior castle walls.
After the conquest of Istanbul it lost much of its strategic importance and was converted into a military hospital.
Over time the area around the castle became settled. Today waterfront houses and old mansions are dispersed among the castle’s ruins. During restoration work which lasted from 1991-1993 it was converted into a museum however it is not open to the public.
Today, Anadolu Hisari is an open air museum but only outer walls can be visited, and the road passes just through it. Admission: Free