They were documented in large numbers around Xian, first in 1912 by the Western traders Fred Meyer Schroder and Oscar Mamen, and also in 1913 by the expedition of Victor Segalen.
U.S. Army Air Corps pilot James Gaussman is said to have seen a white jewel-topped pyramid during a flight between India and China during World War II.
Colonel Maurice Sheahan, Far Eastern director of the Trans World Airline, gave an eyewitness account of his encounter with a pyramid in the March 28, 1947 edition of The New York Times.
The location, reported 40 miles (64 km) southwest of Sian, is in an area of great archaeological importance, but few of the pyramids have ever been explored.
Most are natural hills shaped by man, and they are among the biggest Chinese mausoleums, such as Qianling (乾陵), joint tomb of Emperor Gaozong of Tang and of the Empress Wu Zetian.