The Longyou Caves were only discovered late in the 20th century. At least 24 caves have been discovered so far. All of which were carved by hand. Although the overall excavation involved almost a million cubic metres of stone, there is no historical record of them or evidence of the work. Their origin is a complete mystery. At present there is no explanation for their existence. They represent one of the largest underground excavations of ancient times.:
"Ton of Tea" by Chinese artist Ai Weiwei is just that - a cubic metre of compressed Pur Er tea. Ai Weiwei is a really interesting bloke, active in the arts and political activism, and worth looking up.