In the midst of a 19th-century garden, surrounded by modern sculpture, a federal worker in a stiff white shirt attached a pink admission ticket to his tie. Then he laced up his skates, and began gliding around the ice.

Midway on his clockwise circle, just across from Sol LeWitt's "Four-Sided Pyramid," he began to twirl. Yes, it was a workday. But the opening of the ice rink in the National Gallery of Art Sculpture Garden was just too good to miss.

"If you mention to anyone my being here," he said, "just say Mr. Hillenbrand took a long coffee break."

All day long, kids and tourists and people grabbing idle moments came to the world's only skating rink within a sculpture garden. The garden, which opened in March, already was renowned for successfully integrating art and nature. The rink has added a major new element: The beauty of the human form in motion.

Marina Meehan had brought her daughter to the Mall to see a Vermeer painting at the gallery. Afterwards, when 10-year-old Katherine spotted the rink, the trip turned into a skating expedition.

"It has the feeling of Rockefeller Center," said Meehan, looking out toward the tall marble buildings in the distance. "It's art, it's life--it's terrific."

A somewhat battered rink already sat on the 4.1-acre site at Constitution Avenue and Seventh Street NW before the Morris and Gwendolyn Cafritz Foundation provided $13 million to create the garden. Calvin Cafritz, the eldest son of the couple for whom the foundation is named, said he'd always considered the rink to be an integral part of the site.

But in planning committee meetings, some argued that an ice rink would detract from the grandeur of the art and the tranquility of the garden. They did not see the point, did not want to "waste" the space.

They were overruled.

NGA Director Rusty Powell "was a strong advocate," said the gallery design chief, Mark Leithauser. Powell and Leithauser helped form a majority that argued the aesthetics of skating, the joy of motion. After all, one of the museum's most prized possessions is "The Skater" by Gilbert Stewart.

"Think of Avercamp," Leithauser said, referring to the 17th-century Dutch master who painted winter scenes of skaters sliding along, little kids falling on the ice and throwing snowballs. Before Avercamp, paintings tended to show people posed, stiff and somber. His art, using the motion of skating, was a breakthrough, Leithauser said.

It is so right, he said, that four details from Avercamp's work have been made into banners that hang from the lights that surround the rink.

"It looks great," Leithauser said. "It's lighthearted, and whimsical, like the whole garden."

The gallery's senior architect, James Grupe, came by yesterday to admire the handiwork of a big design crew that included curators, designers, architects, horticulturalists, soil experts, engineers, laborers.

"It changes the whole dynamic of the site. It's alive," concluded Grupe. "There is a level of intrique in seeing the art juxtaposed against the skaters."

Robert and Beverly Christian, of Southwest Washington, frequent sculpture garden visitors, came yesterday specifically to watch the skaters.

"The rink doesn't take away from the art--it adds to it," said Robert Christian. "It will bring a lot of people who would normally not come for the sculpture alone."

At one entrance, skaters catch their first glimpse of the rink through the legs of Alexander Calder's "Cheval Rouge." From another gate, the rink is framed through the arches of Tony Smith's "Moondog." At least seven of the garden's 13 sculptures loom into view as the skaters glide around the icy oval.

The architectural and engineering challenges of creating the rink were monumental.

Just for starters, lockers, a skate rental booth and a Zamboni machine hardly lend themselves to artistic interpretation. The solution: two erectors sets can be taken down each spring.

The demountable buildings--one to house the rental business and one to shelter the Zamboni--are in the style of the familiar pavilion already on the site.

The pavilion itself was designed to evoke Paris metro stations. It currently is being renovated, and will open as a glass-enclosed bistro in the spring.

The rink in other seasons becomes a fountain that arches eight fingers of water skyward that then return to a pond surrounded by marble benches hewn from a Tennessee quarry. A long-closed quarry had to be reopened to provide the color of stone used in the National Gallery's two nearby buildings.

Creating a rink that could be converted into a fountain required fine attention to detail and timing.

The nozzles and other equipment for the fountain, and the machinery for cooling the rink, had to be installed simultaneously into wet concrete that would form the basis for both. Hundreds of tons of concrete were poured within a 16-hour period, without interruption. "Truck after truck lined up throughout the night," Leithauser remembered.

The fountain, a great success with overheated tourists who lingered round it all summer, was turned off and drained as a first step towards yesterday's rink opening. The fountain's pieces all unscrew.

Seasonal light fixtures were installed around the rink. They are smaller versions of the Paris-style lamps that circle the garden pathways. Once the lamps were screwed into holes drilled for that purpose, workmen put steel cables between the lamps, then strung white twinkle lights, in the Tivoli Garden style.

The rink is open Friday and Saturday until 11 p.m., and until 10 p.m. other nights. The sculpture garden, however, keeps regular museum hours (one gate remains open at night).

The sculptures after dark are bathed in light. There will be just one way to see them after 5 or 6 p.m.: Come in winter, and skate.

CAPTION: The ice-skating rink in the Mall sculpture garden attracted tourists and workers when it opened to the public yesterday.

CAPTION: Visiting students from Cape Town, Liane Scheepers, left, Natalie Ladegourdie and Chase Saunders, take a turn on the ice.

CAPTION: Four-year-old Molly Stonier straps on her rental skates in preparation for her debut on the Sculpture Gallery rink.

CAPTION: Stacy Allibone, from New Jersey, gets five fingers from Alexis Young, left, of Vienna, as she passes by.