He wrapped Berlin's Reichstag in a silvery curtain, stretched a pier across an Italian lake that made visitors think they were walking on water, covered trees in woven polyester, and now he's brought 7,506 barrels to the UK. He's 82-year-old artist Christo, and he makes sculpture that's impossible to ignore. To wit, for summer, he has installed a 20-metre pyramidlike (technically it's a trapezoidal prism) structure on London's Serpentine Lake in Hyde Park, which comprises a giant stack of 55-gallon barrels, weighing 600 tonnes, and called it Mastaba - Arabic for ‘bench' - a reference to Mesopotamia and pharaoh's tombs. “It is the visual senses, the wind, the water,” Christo says. “It is real, not the television, not computer images. I love thre real world. I cannot stand the virtual reality.” ( Until Sept 23).