England, London, Tower Bridge viewed from the south bank of the River Thames.

England, London, Tower Bridge viewed from the south bank of the River Thames with an iconic red London bus crossing the bridge.

England, London, Tower Bridge in evening light viewed from the south bank of the River Thames with an iconic red London bus crossing the bridge.

Denmark, Copenhagen, Rosenborg Castle.

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

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, Khiva, Exterior detail of Tash Khauli, also known as Tosh Hovli, Ichan Kala.

Uzbekistan, Khiva, Exterior detail of Tash Khauli, also known as Tosh Hovli, Ichan Kala.

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.