For modern sculpture at its best - don't fence it in

I cannot think of a better way to view modern sculpture than in wide-open spaces. This is especially true if those spaces include beautifully landscaped lawns and wooded areas; dramatic views of distant, low-lying mountains; winding paths that take you easily and at your own pace from one excellent piece of sculpture to the next; and a small museum that includes smaller and more intimate works, preparatory sketches and drawings, and a few paintings.

At least that's what I decided recently after spending an afternoon at Storm King Art Center, the internationally famous, 200-acre, open-air museum dedicated to the exhibition of modern sculpture. The 65-mile drive through rolling countryside and woods from New York City to Storm King's Mountainville, N.Y., location had been pleasant enough, but did little to prepare me for what I was to find at my destination.

I wasn't expecting the beauty and spaciousness of the Storm King grounds, or the consistently high quality of the work on view. It was a profound pleasure to see how well the sculpture of such artists as David Smith, Alexander Calder, Isamu Noguchi, Alexander Liberman - to mention only a few - fitted into this vividly green and well-tended landscape environment, and the way other, smaller works adjusted themselves perfectly to bushes, flat fields, or rocky hillsides.

I thoroughly enjoyed myself and couldn't help but think what a perfect place this would be for anyone having understanding responding to 20th-century sculpture. Above all, the visitor sees outdoor sculpture as it was intended to be seen: uncluttered by other works (all the pieces are widely separated, some by hundreds of feet), and in good, clear light. They can, as a result, be experienced as sculpture, as created objects functioning within real space and not as the cramped, ill-defined, amorphous things they so often are in indoor museums.

Storm King's collection is impressive. It consists of more than 165 works by most of the important sculptors of our time, and is especially rich in sculpture by David Smith (13 pieces); Calder (5 works, including his impressive 56 -foot-high stabile ''The Arch''); and Mark diSuvero (4). Several other major works - including some by Anthony Caro - are on loan to the center.

This summer's visitor to Storm King has a treat awaiting him in the form of a combined outdoors and indoors exhibition of works by the noted British sculptor Barbara Hepworth. It includes one of only two complete editions of the ''Family of Man,'' two major groupings from ''Conversations With Magic Stones,'' and white marble works of the early 1960s.

Storm King will remain open through Oct. 31, daily except Tuesdays from 2 to 5:30 p.m. Requests for information should be addressed to the Center at Old Pleasant Hill Road, Mountainville, N.Y. 10953. Telephone: (914) 534-3115.