The part of the Great Wall built by the Ming Dynasty is also known as the Fourth Great Wall. It is stronger and in better repair than any previous walls, due in part to the better construction techniques it employs.
The wall is made up of baked clay bricks and stone. These materials replace and reinforce the rammed earth used in walls built by the Qin, Han and Sui.
In some places, the wall is wide enough for a car to be driven on it. Portions of its length have been reinforced with double and triple walls that helped strengthen older parts and confuse potential attackers.
The wall averages 6.7 meters, or 22 feet, across the top, though its actual size varies from one location to the next. The Ming Dynasty equipped the wall with guard towers and fortresses located at strategic points. These were manned by soldiers and watchmen who would fire cannon or light smoke signals when an attack from outside occurred.
The wall was reinforced and repaired repeatedly over the course of the Dynasty to defend the Empire against invasions by the Manchu. In 1644, the Manchu were finally able to infiltrate China and pass over the Wall. Construction stopped with the beginning of the Manchu-dominated Qing Dynasty, but the wall was left standing.
As one of the largest man-made structures in the world, the Great Wall is a popular tourist destination. Because of its large size, however, most people visit only a few sites along the way. The most popular tours are one day trips that start from Beijing.
The two most popular sites are Badaling and Juyongguan, but tourists also visit the wall at Mutianyu, Huanghuacheng, Gubeikou, Jinshanling and Simatai. The most photographed part of the wall is located at Juankou, an arrow-shaped mountain farther away from Beijing. This area features many famous sections of the wall, but is much harder for many tourists to reach.
Since the wall stretches across most of China, tourists can also visit it in Hebei, Tianjin, Liaoning, Shanxi, Ningxia and Gansu provinces. Not all areas of the wall have been as well restored as those near Beijing, so hiking or climbing may be difficult or restricted at some locations.
Because the Great Wall of China is so old and has been so inconsistently maintained, some portions of it are in very poor repair. This problem is made worse by constant tourist traffic; over 10 million people visit the Great Wall every year. Many of them take bricks or other pieces of the wall home as souvenirs.
Parts of the wall have been completely destroyed by road construction crews and locals who remove stones for building projects. Sandstorms threaten the part of the wall in Gansu province and other western areas, where significant parts of the wall are still made from mud.
Restoration projects have helped some parts of the Great Wall of China, but hurt other parts. A few of the restorations undertaken for the benefit of tourists are inauthentic and encourage even more erosion. Nearby public utilities, restaurants and other services also cause problems.
About 50 percent of the wall has completely disappeared over the years, while 30 percent remains in ruins. Less than a quarter of the wall is in reasonable condition. In recent years, the Chinese government and international preservation organizations have enacted regulations to stop damage and improve proper restoration efforts. Tourists can contribute by taking nothing from the wall and by making sure they leave no litter behind.
Those interested in visiting the Great Wall from Beijing have several options, depending on which section they want to see. Badaling and Juyongguan can be reached via bus, train or taxi from Beijing. Tour groups that cover the Great Wall, Ming Tombs and other nearby attractions are readily available. Mutianyu, slightly more distant from Beijing, can be reached by a long bus or taxi trip, but not by train.
Other destinations may require taking a special bus for Great Wall visitors, renting a car, or staying in a nearby town overnight, then taking a different bus in the morning. Outside of the immediate Beijing area, visitors to the great wall can take long-distance trains to the closest town, then choose local transportation to visit the Great Wall itself.
In the winter, the cities are much warmer than the area around the Great Wall, with a difference of up to 5 degrees Celsius, or about 9 degrees Fahrenheit. Tourists should bring additional warm clothing to prevent discomfort while they visit the wall.
As the Chinese climate is prone to extreme temperatures, it's a good idea to bring protective clothing suitable for the season on any visit to the Great Wall. Winter temperatures can reach -20 degrees Celsius, or -4 degrees Fahrenheit. Summers can be as hot as 40 degrees Celsius, or 104 degrees Fahrenheit.
Hikers will experience more extreme weather conditions than people who come to see the wall but don't intend to be active around it. Tourists who intend to hike should bring comfortable shoes suitable for loose bricks and uneven terrain, as well as windbreakers for brisk days. Hikers should remember that there is no rescue system in China.
Tourists can engage in many activities at the Great Wall of China. One of the most popular is photography, but more active visitors may also choose to make the 10km, or 6.25 mile, hike from Jinshanling to Simatai, about 130 km, or 80 miles, northeast of Beijing.
In the Badaling section of the wall, visitors can enjoy a trip to the Great Wall Museum. This facility includes walk-through exhibits on the history of the wall, plus many different models and artifacts. Admission is free, though there is a small charge to visit the theater.
At Mutianyu, tourists can also enjoy a toboggan run. Two chairlift lines take visitors to different parts of the Mutianyu Great Wall section. They can choose either a return chairlift rids or a toboggan ride back down from the wall.