Anadolu Hisari (Ottoman Fortification on the Bosphoros Strait)

 

The small castle of Anadolu Hisari, built for Sultan Bayezid I between 1390 and 1395,
was not capable of closing the strait to enemy shipping. Instead, its primary function
was to secure the Asian side of a major crossing point, the Bosphoros being at its
narrowest here, and to dominate the mouth of a small river which could serve as a harbor.
A little over fifty years later Sultan Mehmet I surrounded Bayezid's simple castle with
a curtain wall and towers. Written evidence also indicates that most other structures
within the curtain were of very simple construction, though the mosque added by
Mehmet II might have been more substantial.

1. Central Keep; 2. Inner Court; 3. Inner enciente.

Reference:

D. Nicolle, Adam Hook (illust.), "Ottoman Fortifications, 1300-1710," Fortress 95,
Osprey Pub., Oxford, UK, 2010, P.11