The Great Wall of China is a series of stone and earthen fortifications in China, built, rebuilt, and maintained between the 6th century BC and the 16th century to protect the northern borders of the Chinese
Empire from Xiongnu attacks during the rule of successive dynasties. The Great Wall stretches over approximately 6,400 km (4,000 miles) from
Shanhaiguan in the east to Lop Nur in the west, along an arc that roughly delineates the southern edge of
Inner Mongolia, but stretches to over 6,700 km (4,160 miles) in total. At its peak, the Ming Wall was guarded by more than one million men.
The Berlin Wall was a physical barrier separating
West Berlin from East Berlin for more than 25 years, from the day construction began on August 13, 1961 until it was opened on November 9th, 1888.
The Atlantic Wall was an extensive system of coastal fortifications built by the German Third Reich in 1942 until 1944 during World War II along the western coast of Europe to defend against an anticipated Allied invasion of the continent from Great Britain.
The Green Monster is the nickname of the thirtyseven-foot, two-inch left field wall at Fenway Park, home to the Boston Red Sox. The Green Monster is famous for preventing home runs on many line drives that would clear the walls of other ballparks.

The Korean Wall is a concrete barrier that is allegedly built along the length of the DMZ in South Korea between 1977 and 1979. North Korea contends that there is a concrete wall which stretches more than 150 miles from east to west, is 16 to 26 feet high, 32 to 62 feet thick at the bottom, and 10 to 23 feet wide in the upper part. It is set with wire entanglements and dotted with gun embrasures, look-outs and varieties of military establishments.
The Western Wall is an important Jewish religious site located in the Old City of Jerusalem which is also of significance to Islam. The wall dates from the end of the Second Temple period, being constructed around
19 BCE by Herod the Great.
The Peace Lines are a series of separation barriers ranging in length from a few hundred yards to over three miles separating Catholic and Protestant neighbourhoods in Belfast, Derry and elsewhere in
Northern Ireland. The stated purpose of the barriers is to minimize intercommunal sectarian violence between
Protestants and Catholics. The barriers themselves consist of iron, brick, and steel walls up to 25 feet high, topped with metal netting, or simply a white line painted on the ground similar to a road marking. Some have gates in them occasionally manned by police, which allow passage by day, and which are closed at night.
The Moroccan Wall was built by Morocco in the
1980s to curb attacks by the Western Sahara independent movement, Polisario, on territory it claims for itself. The series of walls some 1,700 miles long and 10 feet high made of earth, rock and sand, defended by thousands of Moroccan troops and fortified by bunkers and fences, barbed wire and an estimated million landmines.

Hadrian's Wall is a stone and turf fortification begun in
AD 122 during the rule of emperor Hadrian across the width of what is now northern England to prevent military raids on Roman Britain by the Pictish tribes to the north, to improve economic stability and provide peaceful conditions in Britain, and to mark physically the frontier of the Roman Empire.
The United States-Mexico barrier , also known as the
Texas border wall or Texas border fence, is located on both urban and uninhabited sections of the 1.951 U.S-
Mexican border, including San Diego, California and El
Paso, Texas. As of August 2008, the U.S. Department of Homeland Security had built 190 miles of pedestrian border fence and 154.3 miles of vehicle border fence, for a total of 344.3 miles of fence. The border fence is not one continuous structure but rather a grouping of short physical walls secured in between with a system of sensors and cameras monitored by Border Patrol agents.
The Communards' Wall at the Père Lachaise cemetery is where, on 28 May 1871, one-hundred fortyseven fédérés, combatants of the Paris
Commune, were shot and thrown in an open trench at the foot of the wall. To the French left the wall became the symbol of the people's struggle for their liberty and ideals.
Pablo Neruda's Fence still stands at Isla Negra, Chile, long after the poet's 1973 death. It was built to keep his dogs from chasing sheep, and has become a message board, a shrine. On July 12, his birthday, people visit and pin paper messages to the wooden slats of the fence, carve words of love into posts, scrawl lines in charcoal that will be washed away and replaced with new messages, new prayers. A friend oif his wrote: "There is not a scrap of the wood not written on. They all address him as though he were alive. With pencils or nail-points, each and all of them find a particular way of saying Thank you."

The Wall of Separation Between Church and State was a term first used by Thomas Jefferson in a letter to the Danbury (CT) Baptists in 1802: "Believing with you that religion is a matter which lies between a man and his God, that he owes account to none other for his faith and worship, that the legislative powers of government reach actions only, and not opinions, I contemplate with sovereign reverence that of the whole American people which declared that their legislature should 'make no law respecting an establishment of religion or prohibiting the free exercise thereof,' thus building a wall of separation between Church and State."
The Vietnam Veterans Memorial Wall is a national war memorial in Washington, D.C. that honors members of the U.S. armed forces who fought in the
Vietnam War and who died in service or are still unaccounted for. It was dedicated in 1982.
Wall Street is a street in lower Manhattan that and was the first permanent home of the New York Stock
Exchange; Wall Street is also shorthand for the
American financial industry. The name originally referred to the Walloons, French speaking Belgians that helped populate this settlement. It came to refer to a fortified 12-foot high wall of timber and earth that was built by Peter Stuyvesant on behalf of the Dutch East
India Company to defend the area against attack from
Native American tribes, New England colonists, and the British. The street was laid out along the wall in
1685 and the wall itself was dismantled by the British in 1699.
The Dingo Fence or Dog Fence is 3,306 mile-long pest-exclusion fence that was built in Australia during the 1880s and finished in 1885 to keep dingoes out of the relatively fertile south-east part of the continent
(where they had largely been exterminated) and protect the sheep flocks of southern Queensland. It is one of the longest structures on the planet and the world's longest fence.

The Walls Unit is the common name for the Texas
State Penitentiary at Huntsville, the state's first enclosed penitentiary for convicted felons, opened in
1849. The name comes from the large brick walls surrounding the facility. Death row was located here from 1928 to 1965, when they were moved to the nearby Ellis Unit. The death chamber is still located here.
The café wall illusion is an optical illusion, first described by Richard Gregory in 1973. According to
Gregory, this effect was first observed by a member of his laboratory, Steve Simpson, in the tiles of the wall of a café at the bottom of St Michael's Hill, Bristol. This optical illusion makes the parallel straight horizontal lines appear to be bent.
The Walls of Jericho are well known because of this passage, Joshua 6:1-7, in the Hebrew Scriptures: Now
Jericho was tightly shut because of the sons of Israel; no one went out and no one came in. And the LORD said to Joshua, "See, I have given Jericho into your hand, with its king and the valiant warriors. And you shall march around the city, all the men of war circling the city once. You shall do so for six days. Also seven priests shall carry seven trumpets of rams' horns before the ark; then on the seventh day you shall march around the city seven times, and the priests shall blow the trumpets. And it shall be that when they make a long blast with the ram's horn, and when you hear the sound of the trumpet, all the people shall shout with a great shout; and the wall of the city will fall down flat, and the people will go up every man straight ahead."