The Longyou Caves were discovered late in the 20th century. At least 24 caves have been discovered so far. All 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. One of the largest excavations of ancient times. Excel in the area of your interest. http://youtu.be/bK7NUdh01WY
"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.
“The World Health Organisation (WHO) says there should be no human exposure to more than 200 micrograms per cubic metre (ug/m3) in any hour. But many places in London have dozens or hundreds of such exceedances every year. Putney High Street suffered a lung choking 1,151 exceedances in 2016.