In 2018, London's Hyde Park was home to Christo and Jeanne-Claude's latest installation: The Mastaba (Project for London, Hyde Park, Serpentine Lake). The temporary sculpture took cues from mastabas of the first urban civilizations of Mesopotamia, which were mud benches with two vertical sides, two slanted sides, and a flat top. Towering at 20 meters high, its 600 metric tons anchored to the Serpentine Lake, this waterborne project gathered 7,506 painted oil barrels to create a floating mosaic of red, white, blue, and mauve. The most ambitious of Christo and Jeanne-Claude's barrel works to date, The London Mastaba is a precursor to the duo's work in progress The Mastaba (Project for Abu Dhabi, United Arab Emirates). First conceived in 1977, The Mastaba for Abu Dhabi, if realized, would be Christo and Jeanne-Claude's greatest achievement and only permanent large-scale work. Situated in the desert and made of 410,000 multicolored barrels, the 150-meter-high sculpture would be the largest in the world, rising higher than the Great Pyramid of Giza. Designed by Lorenza Giovanelli and Christo, this book gathers drawings, collages, technical data, scale models-many published for the first time-and photographs by Wolfgang Volz to trace Christo and Jeanne-Claude's 60-year history of barrel artworks.