The main gallery of the Barnes collection is a high-ceilinged room that faces south. The masterpieces in that room alone would reward weeks of study. There are no mind-numbing descriptions of the art. Barnes wanted his visitors to look, not to read. He arranged the paintings and artifacts so as to illuminate subject matter and formal qualities such as color, light, line and the use of space.

In the main gallery for instance, he placed a portrait by Cézanne of his wife wearing a prim, high-necked dress and hat next to some luscious nudes by Renoir. In another grouping, he positioned Renoir’s cozy depiction of his family tended by a servant beneath Cézanne’s nude, almost featureless bathers in a strange, hostile landscape. Areas of burnt orange in predominantly cool color schemes unite these paintings and others on this wall.

Throughout this room and others, Barnes hung centuries-old metalwork — hinges, keys, locks and metal ornaments — among the paintings. Frequently these objects replicate dominant shapes in the paintings or underscore their subject matter.

On the west wall of the main gallery, for instance, is a Cézanne painting of Leda about to be impregnated by Zeus disguised as a swan — a mythological subject recounted by Ovid in his Metamorphoses. Barnes placed an unusual key with two sharp brackets next to the Leda painting, echoing the way the swan grips Leda’s arm with his beak.

Many of the works in the Barnes collection revolve around sexuality — Matisse’s odalisques, Renoir’s naked maidens, Modigliani’s reclining nude with her provocative buttocks. Barnes’ interest in the naked human body as portrayed in art is not surprising. He was, after all, a doctor by training. In addition, he was born in the late Victorian age and matured during the radical years of the early 20th century when the artists that he admired torched the repressive norms of the Victorian era.

On wall after wall of the collection, fecund females cavort near stout, middle-aged women swathed in voluminous dresses. Many of the doctor’s wall ensembles engender reveries about youth and age, carnality and spirituality as well as about servitude and privilege.

Barnes did not consider his galleries to be a museum. He considered them to be a means of educating people about art while simultaneously giving them the intellectual resources to be productive members of a democratic society. Reflecting his own background — he was the son of a butcher — Barnes particularly wanted to reach blue-collar workers, poor and disenfranchised people, African-Americans and young artists.

Barnes’ interest in African-Americans stemmed from deep empathy. He was born in 1872, just seven years after the end of the Civil War. When Barnes was a child, his mother, a Methodist, took him to African-American camp meetings and revivals. As an adult, he became one of the first major collectors of African art. Beginning in 1947, he formed a close association with Lincoln University, a small, historically black college in Chester, Pa., and stipulated that Lincoln University would nominate four of the board’s five trustees.

To further the doctor’s educational purposes, most of the gallery rooms are equipped with walnut benches so that visitors can observe and meditate on the art. Because of timed admissions, the galleries are uncrowded, contributing to the serenity necessary for contemplation.

The restrained architecture and luxuriant landscaping also contribute to this serenity. A courtyard planted with ginkgo and sweetgum trees is in the center of the building where visitors will pass it as they move from gallery to gallery. Architects Williams and Tsien described their work as “a gallery in a garden; a garden in a gallery.” A team headed by the prominent Philadelphia landscape architect Laurie Olin did the landscape design, referencing aspects of the Barnes arboretum in Merion.

Tod Williams said that at first he and Tsien thought they might be able to expand the galleries by a small percentage, keeping the same proportions. But, he said, they soon found that this was impossible because it would have destroyed the spatial relationships between the carefully hung artwork.

This illuminates the reason why Barnes said that his collection couldn’t be moved from the way he had positioned it and that nothing from it could be loaned or sold. Though he collected the work of the major artists of his time, the collection itself with its carefully constructed wall ensembles was his art. To have moved any part of it would have been like defacing a great painting with graffiti.