Visitors pass by Alexander Calder's "6 Dots Over A Mountain" (1956) at the Denver Botanic Gardens, April 28, 2017.

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Alexander Calder’s sculptures are considered icons and landmarks around the world. Denver Botanic Gardens’ guest curator Alfred Pacquement uses another, more personal, analogy.

“It’s like taking out a part of your body if you take out the Calder,” he says.

That grown sense of attachment partly explains why Denver Botanic heard “no” a lot when it asked other institutions to loan out their Calder sculptures. In the end, the gardens was able to pepper nine works among its plants and pools.

“It certainly would not have been possible to consider this show as a travelling show, because the pieces are so hard to get,” Pacquement says of the show he spent two years putting together.

Pacquement used to direct the Musée d'Art Moderne, in Paris at the Center Georges Pompidou. Calder was an American artist. But he spent a lot of time in Paris, where he had a studio that Pacquement now oversees.

“He has done a huge range of sculptures, jewelry and drawings,” he says. “But this selection is exclusively on monumental pieces.”

As an artist, Calder pioneered different types of sculpture. Denver Botanic’s exhibition spans the last two decades of his career before he died in 1976. During that time, known as his “monumental” period, he focused on making large, metal sculptures.

This all makes Calder one of the most important 20th century artists, says Rebecca Hart, contemporary art curator for the Denver Art Museum.

“There are very few places in the world that you can go and see nine Calder sculptures in one hour,” she says.

A woman walks by Alexander Calder's standing mobile, "Polygons on Triangles" (1963), reflected in a pool at the Denver Botanic Gardens, April 28, 2017.

Corey Jones/CPR News

Hart has worked with five of Calder’s monumental sculptures during her career. That includes the 17-ton “Young Woman And Her Suitors” at the Detroit Institute of Arts. These pieces can be very expensive and difficult to move, she says. They also leave big, empty spaces that most places don’t know what to do with.

That didn’t stop the Denver Art Museum from lending its Calder sculpture to the Botanic Gardens. “Snow Flurry, May 14” is one of Calder’s signature mobiles; just like what you’d find over a baby’s crib, but bigger and more elegant, Hart says. Calder made Snow Flurry, with its metal rods and white discs, in 1959.

A similar “Snow Flurry” sculpture sold five years ago for more than $10 million. Hart says the museum agreed to lend its Calder sculpture to the Gardens under specific conditions to protect the work from humidity and light. So it’s the only Calder on display indoors.

You’ll find the rest, from cities like Houston, New York and St. Louis, out in the gardens. Two of these sculptures have parts that move with the wind. The others are stationary and known as “stabiles.” Some are figurative, others look more abstract. “The Crab” is a bright red sculpture that stands 10-feet tall with legs that arc down to the ground.

The metal doesn’t move, but it’s many curved lines give it “tremendous energy,” says Calder Foundation president, and Calder grandson, Sandy Rower. And that makes the piece playful. The artist was a serious man who wanted his art to be uplifting.

“He didn’t like art that was too psychologically dark,” Rower says. “He felt that we all experience that in life, we don’t need more in art.”

Alexander Calder's "The Crab" (1962) is one of nine of the artist's monumental sculptures on display at the Denver Botanic Gardens through Sept. 24, 2017. Calder typically titled his abstract sculptures after he built them, simply as a means of identification.

Corey Jones/CPR News

Alexander Calder often reinvented himself, early on with wire sculptures, then his mobiles, and later his monumental works. He was the first artist regularly commissioned to make modern sculptures for public spaces, Rower says. That includes the first sculpture commissioned as part of the National Endowment for the Arts’s public art program.

Calder’s art appears in plazas and museums around the world, and Lisa Eldred, Denver Botanic Gardens’ director of exhibitions, art & interpretation says it’s a good fit for the Botanic Gardens too.

“It’s really something that is part geometric, part organic,” Eldred says. “It makes you question, and it can stand up to both nature and the manmade environment.”

Denver Botanic Gardens’ Calder: Monumental runs through Sept. 24, 2017.