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

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

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

England, County Durham, Durham, Entrance to Durham Castle.

Egypt, Alexandria, Citadel of Qaitbay, also known as Fort of Qaitbay.

Egypt, Alexandria, Citadel of Qaitbay, also known as Fort of Qaitbay.

England, London, The White Tower, Tower of London.

England, London, The White Tower, Tower of London.

Mexico, Anahuac, Teotihuacan, Detail of architectural crenellation representing a bird on display in the site Museum.

Italy, Sicily, Taormina, Piazza Del Duomo and Corso Umberto, Cathedral of San Nicolo and baroque fountain.

Italy, Sicily, Taormina, Piazza Del Duomo and Corso Umberto, Cathedral of San Nicolo and baroque fountain.

Italy, Sicily, Palermo, Cathedral.