Great Wall facts
Los Angeles Times
Purpose: To protect against invaders from the north.
Claim to fame: Longest structure ever built; symbol of China’s violent conquests and architectural acumen.
Construction start: fifth century B.C., though estimates vary.
Length: About 4,000 miles, though estimates vary.
Base width: 15 to 40 feet.
Height: 20 to 50 feet.
Building materials: Stone, brick and earth.
Named UNESCO site: 1987.
Sources: Encyclopedia Americana, World Book