Cai Guo-Qiang's Explosive Artworks.

Chinese artist Cai Guo-Qiang has an unusual choice for art medium: gunpowder. The first picture is from an installation called Spider Web, which took place in Hangzhou, China in 2002. The second one, called Red Flag, took place in Warsaw, Poland in 2005.

Plenty more at Guo-Qiang’s excellent website: Link | Gallery (the navigation is confounding: try clicking on the blinking squares on the top right corner).