In the near-decade of its existence the atrium of I.M. Pei's National Gallery East Building has proven to be an altogether splendid space, but never has it looked so appealing as today, enlivened not only by people moving this way and that but also by a vivid sprinkling of modern sculptures (most of which stand still).

The occasion is the opening of an exhibition of 73 works selected from the collection of Patsy and Raymond Nasher of Dallas, an excellent collection that is all the more remarkable for having been largely put together in the last four or five years. The exhibition is not encyclopedic but it touches many key 20th-century bases, and most importantly the quality of the individual pieces is high.

There's an electric charge between the sculptures and Pei's dynamic space. Obviously, much of this complementary relationship has to do with scale. Being able to view the bridges, balconies and the great space-frame roof as they appear in changing relation to, say, a slender stele by Ellsworth Kelly, or David Smith's proud chariot, "Voltri VI," or Barbara Hepworth's huge green-patinaed bronze, "Squares With Two Circles (Monolith)," enhances our appreciation of the architecture. And the same is true in reverse -- we see these pieces more sharply because of the spaces they inhabit.

But the effect also has to do with the variety of the works -- in age, material, style, size -- and to the appropriate settings created for them by National Gallery exhibits designers and horticulturists. This interior space has never lacked interest -- it's a walk-in abstract sculpture of unusual configuration, sizable dimension, superb materials and ever-changing presence -- but there's more there therenow.

With changing lights and two simple, temporary partitions, a roomlike space for smaller abstract works was separated from the light-filled volume on the ground floor; green-planted "islands" help to make a similarly intimate environment for figurative works on the mezzanine; just a few well-chosen pieces, notably Jonathan Borofsky's giant "Hammering Man," convert the below-ground plaza into a spellbinding place; and for the first time since the opening of the building in 1978, doors to the exterior "room" on the Pennsylvania Avenue side have been unlocked and visitors are free to go outside to enjoy artworks there.

The show is announced at the entrance to the East Building by two contrasting pieces: George Segal's "Rush Hour," an eerie, ironic, contemporary replay of Rodin's "Burghers of Calais" (like Rodin's piece, Segal's consists of six standing figures, but his are more like sleepwalkers than heroes), and Tony Smith's "The Snake Is Out," a muscular exercise in solid geometry and black-painted steel. Smith, who died in 1980 before this version of his 1963 piece was fabricated, was trained as an architect, and it shows here. He and Pei are speaking the same abstract language.

One of the unusual aspects of the Nasher collection, foretold by Segal's moody piece, is its emotional breadth: These Texas collectors (he's a real estate developer, she's active in a variety of cultural organizations) are in love with beauty but not afraid of edginess. Borofsky's "Hammering Man," for example -- a standing figure, 20 feet tall, cut from sheets of black-painted steel, with a motor-driven right arm moving ceaselessly in hypnotic, mindless rote -- is an unforgettable, disturbing reminder that all is not well with the world.

"Hammering Man," made just a couple of years ago, is a direct descendant of Alberto Giacometti's postwar race of emaciated figures. One can see that clearly by comparing him to Giacometti's bronze "Venice Woman III" in the Nasher collection or to "Walking Man II" in the National Gallery's permanent display. Giacometti's figures seem almost ennobled by their isolation; Borofsky's man, by contrast, seems bereft of hope. But there are formal similarities and emotional ones, despite differences in size, material and technique. Note, for instance, the way Borofsky adapted Giacometti's use of extra-large feet to give his slender figure a palpable sense of gravity.

The exhibition offers a feast of such formal and thematic comparisons and contrasts. Magic moments abound. On the ground floor there is an exhilarating sequence of variations on the theme of verticality in pieces by Barnett Newman ("Here III"), Kelly (that untitled stele), and Smith ("Voltri VI"). One cannot help but feel that Smith, perhaps subconsciously, had Newman's paintings in mind when he made his surprising chariot carrying two thin steel "clouds" -- the negative space between them is very like one of Newman's famous "zips." Newman, ironically, was reversing the procedure, converting negative space to positive in a free-standing, undecorated, stainless steel column. Smith's piece is much the more resonant of the two, but Kelly's work gains in the juxtaposition -- the last word in elegance, this tall, thin, mushroom-shaped sheet of steel makes the space around it come alive.

One of my favorite juxtapositions here is that of Picasso's 1950 "Pregnant Woman" with Gaston Lachaise's earlier (1912-27) "Elevation." The subject of both is a standing female nude, but where Lachaise's giantess is all untouchable grace -- she almost levitates, so effortlessly does she balance on her delicate toes -- Picasso's woman is a complex, atavistic icon. Eminently touchable, she seems to come from the earth; her toes are but melted puddles. Nearby is Rodin's troubled "Eve," a third, contradictory, male vision of the woman as object of contemplation and art.

In each of these works, and in many other female nudes in the show, the sense of the otherness of the subject is different but tangible. One would have to be very narrow minded, however, to interpret any of these works as a sexist statement. There is always a sense of otherness -- not sexual but human -- when a great artist struggles to interpret the presence of another human being. Witness, here, Giacometti's extremely moving portraits of his brother Diego -- each of the three half-figures is the same person, and yet each is different; in each we sense not only the mystery of the subject, but of the artist, too, and his Rembrandtian efforts to penetrate beyond mere likeness. The subject becomes not Diego Giacometti, but the metaphysical distance -- as vast as the cosmos, as thin as a hair -- between the artist and the sitter.

There are nine Giacomettis in the show, the most exceptional of the individual groupings in the Nasher collection because it very nearly encapsulates his entire career (other artists shown in strength are Matisse, Duchamp-Villon and David Smith). "Spoon Woman" (1926-27) comes first, a powerful version by the young Giacometti of a persistent 20th-century theme -- the influence of nonwestern sources, in this case definitively African, upon western art. "No More Play" (1931-32), a dry, pocked landscape with totemic figures whose power transcends their tiny size, is a visionary piece of work that spawned a rich progeny, from Isamu Noguchi to Joel Shapiro. "Head (Skull)" (1934) is a superb marble, a moving essay in cubistic solid geometry that authoritatively updates the memento mori (contemplation of death) tradition. And then comes a memorable parade of his postwar figures.

The Nasher collection is full of provocative riches; it is worth many visits for itself and for the way it brings Pei's spaces into crisp new focus. Fortunately, there is ample time. The show will remain on view until Jan. 3. The exhibition was supported by Northern Telecom; it is accompanied by a 210-page catalogue, published by Rizzoli and containing essays by Steven Nash of the Dallas Art Museum (where the show opened), Nan Rosenthal of the National Gallery, Robert Rosenblum and Elizabeth Frank.

And the exhibition offers a first-time opportunity to visit that outdoor "room" on the East Building's north side. This space has an interesting history. Pei conceived of it as a contemplative place in the manner of a Japanese dry garden -- a space to be looked upon, not occupied -- with the difference that he designed it with a quiet, reflective pool of water atop beautiful black stones. This scheme was aborted when the water leaked upon exhibition spaces directly below. Since then it has gone through a number of permutations, none of them wholly successful. But it's a wonderful, inviting, walled space, intimate but open to the light, air and background noise of the city. One hopes that this experiment will stimulate the gallery's staff -- or Pei himself -- to devise a way to keep the doors open.