There are many walls out there. The list below shows other walls that have been built either as defensive structures in a broad definition, or as a means of defining a real or imaginary border.
The Berlin Wall
The Berlin Wall was build as a result of the subdivision of Germany after the second World War, and the subsequent tensions between the Allies and the Soviet Union. For many it was a living symbol og the Cold War. Construction started in 1961, and it was finally torn down in 1989. The East German guards were issued with shooting orders designed to stop people in the border zone at all costs. The wall was 140 kilometres long and 3,5 metres high. Between 150 and 200 people are believed to die attempting to cross the heavily guarded border in the 28 years it stood.
Hadrian’s Wall was built to defend the Roman Empire against attacks from the Pict tribes in the North. The construction began in AD 122 while Hadrian was the Roman emperor. As with the Great Wall of China, in addition to functioning as a defensive structure, it served as a customs- and tax facility. Much of Hadrian’s wall is well preserved, and can be seen in Northern England. The wall was 117 kilometres long, and 3 to 5 metres high. The wall was occupied by the Romans until they withdrew from Britain in 410.
The Moroccan Wall
The Moroccan Wall is a little know defensive structure that stretches 2500 kilometres from the South of Western Sahara to South-Eastern Morocco. The wall is built mostly on Western Saharian land, and separates the country into a Moroccan controlled and a Polisario controlled area. The series of walls were built from 1981 to 1987, after Spain ended its occupation of the country in 1975. There has been extremely little attention to this occupation in the so called Western world.
The Great Wall of Gorgan
This wall is sometimes also called the Barrier of Alexander after Alexander the Great. Among archaeologists it is known as The Red Snake because of the colour of its bricks. The defensive structure lies in the northeastern part of Iran and is 195 kilometres long and between 6 and 10 metres wide. It appears to have been built with the same “loess” material that large parts of the Great Wall have been built with. Dating wise, there is not great accuracy yet. Carbon dating sets the building of this wall to 5th or 6th century A.D.
Here is an interesting article about the wall.
The best way to defend a city is to construct a wall around it. There are many thousands of city walls around the world.
The Korean Wall
The Korean wall is 248 kilometres long and separates North- and South Korea. It is know as the most heavily guarded wall in the world. A demilitarized zone was created between the countries at eh end of the Korean War in 1953. The wall itself is 5 to 8 metres high and was built in 1977 along the demilitarized zone.
The West Bank barrier
The West Bank barrier will be about 700 kilometres long at the end of completion. It separates the West Bank from the areas around. The Israeli government started building it as a measure to reduce the number of suicide attacks. It is probably the most controversial of all walls at this date, and has been deemed contrary to international law by the International court of justice. The wall itself is for the most 8 metres high, and about 60% of the wall has been built. Construction started in 2004.
United States – Mexico Barrier
The United States – Mexico Barrier was built to keep control over the illegal immigration and drug trafficking from Mexico to the United States. The border is 3140 kilometres long, and the barrier fence does not cover the entire border. It has been built in the places where there have been most illegal crossings, but for instance in the Sonoran desert, there is no fence as getting to the closest road means crossing 80 kilometres of desert. The wall is also controversial as amongst other issues three Native American Nations areas are located in the border areas, and many wildlife migration routes pass through the area.