Uzbekistan, Bukhara, Outer walls of the Ark Fortress, Registan Square.

Uzbekistan, Bukhara, Entrance, outer walls and viewing gallery of the Ark Fortress, Registan Square.

Uzbekistan, Bukhara, Entrance, outer walls and viewing gallery of the Ark Fortress, Registan Square.

Uzbekistan, Bukhara, Entrance of the Ark Fortress, Registan Square.

Uzbekistan, Khiva, Kunya Ark, also known as Kohna Ark, housing Museum of Ancient Khorezm, Ichan Kala.

Uzbekistam, Khorezm, Toprak Kala Fortress, Ellik Kala.

Uzbekistam, Khorezm, An ancient wall at Ayaz Kala Fortress 1, Ayaz Kala.

Uzbekistam, Khiva, Akshi Bobo, a tower of Kunya Ark, on left, and outer wall of Ichan Kala.

Uzbekistan, Khorezm, Ayaz Kala Fortress 2, photo taken from Ayaz Kala Fortress 1, Ayaz Kala.

Uzbekistan, Khorezm, Ayaz Kala Fortress 1 above and Ayaz Kala Fortress 2 below, Ayaz Kala.

Turkey, Ayasuluk Castle on Ayasuluk Hill behind the ruins of Saint John’s Basilica, Selcuk, near Ephesus.

England, County Durham, Durham, The Keep, Durham Castle.