Christo and Jeanne-Claude's Umbrella Project in 1991 was the most ambitious and expensive project they have ever undertaken. 1340 blue six metre umbrellas were assembled and erected throughout a narrow valley in rural Japan. 7000 yellow umbrellas were similarly prepared across the Pacific in a dry expanse of Californian land. After months of gruelling process, the two countries united as the forest of umbrellas were opened simultaneously on both continents.