Massive sculpture opens in Spain
(CNN) -- What is billed as the world's largest permanent indoor sculpture has opened to the public at the Guggenheim Museum in Bilbao, Spain.
"The Matter of Time," by American artist Richard Serra, was commissioned by the museum to fill a 32,000-square-foot gallery.
The work of steel is more than 430 feet long, nearly one-and-a-half football fields, and weighs approximately 1,200 tons.
The sculpture comprises eight separate works made from steel pieces more than 14 feet high. Seven of the pieces are new and have been added to an existing Serra work, "Snake," a 1997 piece previously installed at the building.
The $20 million installation is one of the most ambitious, and expensive, in modern history.
"The subject of the work is your experience, your walking," Serra said in April at the unveiling of his model in New York.
"The piece is predicated on walking and moving, anticipation and reflection, through these various pieces and through the museum as a whole."
Over the coming decade, the steel is expected to oxidize, changing color from gray to orange, and finally, amber.
Serra, 66, is known for his monumental sculptures made of nontraditional materials, such as fiberglass, rubber or steel. His work has been shown all over the world, and regularly at New York's Guggenheim Museum since 1969.
The Bilbao gallery was constructed to bear weights of this size, said Thomas Krens, director of the Guggenheim Foundation.
"We think that he is one of the greatest, if not the greatest, living American artist, and this piece and our commitment to Richard is a reflection of that," Krens said.
From San Francisco, Serra is a graduate of Yale University and the University of California. He lives in New York City and Nova Scotia, Canada.