Spanish abstract artist Miquel Barcelo used more than 100 tons of paint with pigments from all over the world, and worked with architects, engineers and even particle physics laboratories to develop the extra-strength aluminum for the dome.
"On a day of immense heat in the middle of the Sahel desert, I recall with vivacity the mirage of an image of the world dripping toward the sky," Barcelo says. "Trees, dunes, donkeys, multicolored beings flowing drop by drop."
The Spanish Foreign Ministry says the government is funding 40 percent of the costs, with the rest footed by private-sector donors. Of the public money, 500,000 euros (US$633,000) comes from a budget for overseas development aid and international organizations like the United Nations.
Spain's conservative opposition Popular Party complained that this means money was diverted from projects to alleviate poverty and boost health care in poorer countries, but the ministry insists the funding for Barcelo's work was separate.
The dispute reached Parliament last week, with Popular Party lawmaker Gonzalo Robles asking "how many thousands of children could have been looked after" with the money spent on the artwork.
The ruling Socialists accused him of twisting the facts.
A Tuesday news conference with Barcelo and Spain's foreign minister was canceled in Geneva. The government also has not said how much it paid the artist for the commission.
The Spanish mission in Geneva declined to comment.
At a ceremony with Spain's King Juan Carlos, U.N.
Secretary-General Ban Ki-moon thanked Barcelo for putting his "unique talents to work in service of the world."
"The artwork you have created for this room is innovative and radiant," the secretary-general said. "I have no doubt that people will come to see it whether they have business here or not."