Strong walls of Ichon-Qala (Itchan Kala) Fortress, UNESCO World Heritage Site, Khiva, Uzbekistan, Central Asia

Alcazaba towers and walls, Almeria, Andalucia (Andalusia), Spain, Europe

Majestic medieval castle with stone bridge over a river, surrounded by wild nature under a cloudy sky, Eilean Donan, Dornie, Scotland, United Kingdom, Europe

Sea walls of the Old City of Akko, Israel

Majestic medieval castle on a hill with cloudy sky at dusk, showcasing historical architecture, Northumberland, England, United Kingdom, Europe

Dunstanburgh castle on Northumberlands coast near Craster.

Dunstanburgh castle on Northumberlands coast near Craster.

Carlisle Castle, Carlisle, Cumbria, England, United Kingdom, Europe

Carlisle Castle in Cumbria, England, United Kingdom, Europe

Old iron cannon and guardhouse on the strong walls of the historic fortress of Farol da Barra in the city of Salvador, Bahia, Brasil

Sacsayhuaman a huge, hilltop, Inca fortress built in the 15thc above Cuzco with zigzag battlements constructed of immense stones, Highlands, Peru

View of Dunluce Castle on cliffs and Atlantic Ocean in Ireland, UK

View of Dunluce Castle and Atlantic Ocean in Ireland, UK