United States President Barack Obama on Wednesday joined other foreign leaders to leave his footprints on the Great Wall, a Chinese landmark in the northwestern suburb of Beijing.

Obama's tour to the Great Wall during his last day in China gave the U.S. president another chance to learn more about the ancient Chinese civilization before leaving for the Republic of Korea Wednesday afternoon.

The Great Wall was the second sightseeing place for Obama during his visit to China. He toured the Imperial Palace Tuesday after a bilateral meeting with President Hu Jintao.

Built originally as the biggest defense work in ancient China, the Great Wall today has become one of the must-see places for visiting foreign leaders to the country in the past six decades.

One of the greatest architectural miracles in human history, the Great Wall stands as the most popular tourist attraction in modern China.

The Great Wall is listed among the UNESCO's World Cultural Heritage sites given its historic status.

Separated sections of the Great Wall were built as early as 2,000 years ago by small kingdoms to defend against raids from nomadic tribes to the north.

When Emperor Qinshihuang, the country's first emperor, united China for the first time in 221 B.C., he ordered the separate sections linked together, forming a complete military defense system.

The Great Wall as we see it today was mostly rebuilt during the Ming Dynasty (1368-1644).

With its sections stretching from northeast to west China, the Great Wall now runs 6,700 kilometers long and its section at Badaling is the first part that opens to tourists.

The wall at the Badaling section averages seven to eight meters in height, six to seven meters in thickness, with a width of four to five meters on top.

The Badaling section runs about 3,741 meters on a mountain of about 700 to 800 meters above sea level, dotted with 19 beacon towers.

Over the past six decades, more than 450 heads of state and government have visited the Badaling section, including former U.S. President George W. Bush and his wife Laura, who toured the same section in 2002.