Fortress of Europe

View looking north at the southern walls of the Fortress of Europe. Mehmet II built this fortress in 1452 in preparation for his conquest of Constantinople in 1453. 

It is built at the narrowest point of the Bosphorus—where it is only 0.5 mi. [0.66 km.] wide.  From here the canons of Mehmet controlled the northern approach to Constantinople.  After the conquest, it was used as a prison.

In the background, right of center, a portion of the span of the Fatih Sultan Mehmet Bridge is visible—this is the northern most of the two bridges that span the Bosphorus.