Beijing's Forbidden City Built on Ice Roads
Ice sledges carried monumental stones to the Forbidden City in the 15th century.
A World Heritage Site, the Forbidden City in the center of Beijing was the seat of Chinese imperial power from 1416 to 1911. Once forbidden to outsiders, the city's palaces were built of massive stones in the 15th and 16th centuries. (See "Forbidden City—China.")
"How in the world did they get these massive rocks to Beijing?" says Princeton engineer Howard Stone, a co-author on the Proceedings of the National Academy of Sciences report. "It raises tremendous engineering questions."
Carved with dragons and clouds, the "Large Stone Carving" that graces the stairway to the Hall of Preserving Harmony, for example, weighs more than 300 tons (272 metric tonnes).
A tourist attraction today, the Large Stone Carving is 55 feet
