How'd They Do That? The Story Of A Giant Rock And A Road Of Ice
Huge stone slabs weighing up to 300 tons that now reside in Beijing's Forbidden City were slid more than 40 miles in 15th- and 16th-century China over water-lubricated ice roads in the dead of winter. Though spoked wheels had been around for almost 3,000 years, the ice roads were smoother and required less manpower.