Defensive walls were common from the ancient period into the medieval period. Generally, these are referred to as city walls or town walls, although there were also walls, such as the Great Wall of China and the Atlantic Wall, which extended far beyond the borders of a city and were used to enclose vast regions.
City walls were still occasionally used as late as the 19th century, although by this time they were generally of wood (rather than stone) construction and used only around small frontier settlements. City walls also had towers and were frequently surrounded by trenches.
The practice of building these massive walls had been developed sometime before the rise of the Sumerian Empire and was connected with the rise of city-states.
Often the walls proved impenetrable to attacking armies which then laid siege to the city.
Within walled cities, the poor and "noxious trades" were generally located near or outside the walls.
Chinese cities occasionally have remnants of city walls that were built in the Ming Dynasty and designed to withstand artillery bombardment. Chinese cities generally outgrew their walls, which fell into disrepair in the Qing dynasty. The city of Xi'an has well-preserved walls with a water filled moat that is a tourist attraction incorporating small parks surrounding a busy and modern area of the city.
The walls of Beijing were demolished during the 1960s to open large streets around the city. A metro line also follows the location of the former city walls.
Stone walls built in 14th-16th century, at the isthmus of the Pelješac peninsula, to the north of Dubrovnik; 890 meters long town wall and 5 km Great Wall outside the town
Karlovac city walls, built in 1579 as a six-point star with bastions.
The walls of Akko (Acre) - 18th century modern Ottoman fortification able to withstand cannons attack. The wall has been restored and now includes rampart for tourists.
Five different sets of walls have been built around the city of Constantinople, the most important of which was the last, built under the reign of Theodosius II, who came to power in 408 AD.
Also known as the wall of Anthemius, it was erected in 413 AD, and stretched across the peninsula, protecting the city from a land invasion.
Dimensions of the walls were taken partly from first hand measurements of the walls in present day Istanbul and partly from various resources on the Princeton Campus.
The southern wall of the city was demolished, to extend the city limits nearly to the river.
As Christians from the north drew nearer to Cordoba, conquering Toledo in 1085, the city's new rulers reinforced its defenses.
In the 14 th century, however, the citywalls were extended to enclose a new area to the southwest, including the Alcazar de los Reyes Cristianos, la Huerta del Alcazar and the Alcazar Viejo (San Basilio neighborhood).