The Great Wall of China
This 4,160-mile wall was built to protect China from invading Huns, Mongols, and other tribes, and to unite fortifications into one defense system. Begun in the 7th century B.C., the barricade took hundreds of years to build, and ranks as the world's longest man-made structure-and is apparently the only one visible from space.
This ancient capital city was built around 9 B.C. during the reign of King Aretas IV and continued to flourish during the Roman Empire. It is now visible in its pink stone ruins and carved façade.
Standing 125 feet tall atop the Corcovado Mountain high above Rio, this statue took five years to build. Constructed in France by sculptor Paul Landowski, it was shipped to Brazil in pieces, and then carried up the mountain by train, where it was reassembled.
This "city in the clouds" was built 8,000 feet above sea level in the 15th century by Incan emperor Pachacutec. Abandoned by the Incas, the city remained unknown until it was rediscovered by an explorer in 1911.
Pyramid at Chichen ItzaMexico
The center of Mayan civilization in its day, Chichen Itza is still visible in several structures, including the pyramid of Kukulkan.
This giant, 50,000 seat amphitheater in the center of Rome was built over 2,000 years ago, and still influences the design of sports stadiums worldwide.