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 thirty-seven-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.