Dr. Robert R. Wilson, a physicist who built the world's most powerful particle smashers in a setting that he insisted be surrounded by restored prairies and enriched by striking architecture and objects of art, died on Sunday at his home in Ithaca, N.Y. He was 85.

With a career that began in the 1930's, Dr. Wilson became one of the most important figures in the history of the development of particle accelerators, which smash subatomic particles together at high energy for the study of their interactions and composition.

Though he was involved in numerous breakthroughs in physics research and accelerator design, perhaps his crowning achievement came when he led the design and construction of the Fermi National Accelerator Laboratory in what was then farmland west of Chicago.

Fermilab, as it is known, began operating in 1972 as the most powerful accelerator in the world. And because of the futuristic technologies then embraced by Dr. Wilson, the laboratory has been able to increase its energy over the years and is expected to remain the world's most powerful until 2006, when it will be superseded by the Large Hadron Collider, an accelerator under construction at the CERN laboratory in Geneva.

Besides his scientific achievements, Dr. Wilson was known for the environment he created at the Fermilab site, with hundreds of acres of restored prairie, a herd of bison, fishing holes, abstract sculpture and a central building modeled, in spirit at least, on the Beauvais Cathedral in France.

''When he created Fermilab, it certainly had a style,'' said Dr. Leon M. Lederman, the Nobel Prize-winning particle physicist who succeeded Dr. Wilson as director of the laboratory. ''He was a showman in that sense; he took chances.''

Energy Secretary Bill Richardson said Dr. Wilson had had ''an unerring sense of what is important to the science of high-energy physics and its importance to the nation.''

Robert Rathbun Wilson was born on March 4, 1914, in Frontier, Wyo. Though he tinkered with pumps and vacuum tubes as a boy, he apparently took plenty of time to enjoy the outdoors.

''He always had big, wild tales about being a cowboy in Wyoming,'' said Dr. Dale Corson, a particle physicist and former president of Cornell University, who had known Dr. Wilson since the 1930's. ''Most of them turned out to be true.''

Dr. Wilson received a bachelor's degree from the University of California at Berkeley in 1936 and remained there for graduate school. His scientific style became clear early on, said Dr. Corson, who was also a student there at the time.

Dr. Corson said Ernest O. Lawrence, the legendary inventor of the particle accelerator called the cyclotron, assigned a problem in a Berkeley physics course that no student but Robert Wilson managed to solve. The problem involved finding the strength of the electric fields inside the cyclotron. While most of the students tried to perform difficult calculations to find the fields, Dr. Wilson quickly built a simplified model of a cyclotron in a physics laboratory and measured the electric fields.

''That was his hallmark: a completely ingenious way of solving the problem,'' Dr. Corson said. ''And that carried right up to the Fermilab machine.''

Dr. Wilson went on to do research on the cyclotron with Lawrence before joining the Manhattan Project to develop the atomic bomb. He had stints at Los Alamos National Laboratory and Harvard before becoming the director of the Laboratory of Nuclear Studies at Cornell in 1947.

While at Cornell, he did experiments on the structure of protons that were later explained by the theory that they are constituted of smaller particles called quarks, Dr. Lederman said.

In 1967, Dr. Wilson took a leave of absence from Cornell to become the founding director of Fermilab, where he left his mark as a brilliant designer of the powerful magnets necessary to confine the fast particles as they whirled around a giant ring.

He created the natural, architectural and artistic amenities in part to attract good scientists to the Illinois cornfields and in part because of an innate sense of aesthetics, said Dr. Boyce McDaniel, a longtime friend who is a retired Cornell physicist.

Dr. Wilson's design of the tunnel through which the particles raced at Fermilab included plenty of space to allow for technical improvements. That space came in handy when superconducting magnets, a powerful innovation that Dr. Wilson pushed to develop, were later installed, allowing the lab to boost its energy.

His dislike of bureaucracy was legendary and fit with his sometimes contrarian nature, said Dr. Michael Witherell, Fermilab's current director, who has a handwritten note from Dr. Wilson that reads in part: ''An all too common failing of large institutions is to fall into the bureaucratic morass -- complicated procedures, red tape and all that. That's terrible.''

Dr. Wilson is survived by his wife, Jane; three sons, Daniel, of Indianapolis, Jonathan, of Columbus, Ind., and Rand, of Boston; a sister, Mary Jane Greenhill of Palos Verdes Estates, Calif.; and four grandchildren.

Dr. Wilson was known for completing huge projects ahead of schedule and below budget, but he resigned as director of Fermilab in 1978 because he did not believe that the government was financing it generously enough. He also once lectured a joint committee of Congress on why basic science was crucial even when it did not lead to instant practical benefits.

At the hearings, in 1969, Dr. Wilson's feistiness was most on display in an exchange with Senator John O. Pastore of Rhode Island. When Senator Pastore pressed Dr. Wilson on whether the knowledge gained at Fermilab would enhance national defense, Dr. Wilson said, ''It has nothing to do with defending our country, except to make it worth defending.''

Photos: Fermilab and its surroundings, including the sculpture at left, were largely the creation of Dr. Robert R. Wilson, its first director. (Fermilab); Dr. Robert R. Wilson (Charles Harrington/Cornell University, 1984)