Ancient ice road technique discovered

Chinese engineers used an ice-lubricated road to transport massive stone blocks during the construction of the Forbidden City, avoiding the need for wheels, engines, or cranes. This method was revealed in a study published in the journal PNAS and based on a 500-year-old Chinese document.

Study details historical transport method

The study, titled Ice lubrication for moving heavy stones to the Forbidden City in 15th- and 16th-century China, was authored by Jiang Li, Haosheng Chen, and Howard A. Stone. It describes how a thin layer of liquid water on an icy surface reduced friction, making it easier to move the stones with fewer workers.

Massive stone transport over 70 km

A single stone block measuring 9.6 meters by 3.2 meters by 1.6 meters, weighing about 123 tons, was moved from the Dashiwo quarry in the Fangshan district to the Forbidden City over a 70-kilometer route. This operation occurred between the winter solstice and the end of January, when Beijing temperatures averaged around minus 3.7 degrees Celsius.

Efficient use of ice pits

Pits were dug every 500 meters along the route to maintain a lubricating water film, reducing the workforce needed from 1,500 to fewer than 50 men. The sledge used to drag the stone moved at approximately 8 centimeters per second to keep the liquid water under the load.

Historic stone in the Forbidden City

A carved stone block weighing over 300 tons, known as the Large Stone Carving, is displayed in the Hall of Preserved Harmony within the Forbidden City grounds. The construction of the Forbidden City began in 1406, though some sources suggest it started in 1417.

Exhibition highlights historical methods

The technique of using ice roads to transport heavy stones has been featured in an exhibition titled A Century of Stewardship: From the Forbidden City to the Palace Museum, which marks the 100th anniversary of the Palace Museum, established in 1925 on the site of the Forbidden City.

Palace Museum sees record attendance

The Palace Museum saw its visitor numbers exceed 10 million for the first time in 2009 and reached 17.6 million in 2024, showing a significant increase in public interest in its historical collections and exhibitions.