It's a big new store on sidewalk level at an extraordinary corner, but even on busy days one can walk by it without noticing, in part because, despite its size and lots of glass, it's so low key as to be practically invisible, and in part because it's altogether unexpected.

Who, after all, would anticipate the Starfields of Astraea, an elegant offbeat 24-hour bookstore right on Pennsylvania Avenue at 13th Street NW, across from Freedom Plaza and the Federal Triangle, perhaps the most prominent spot in the whole new downtown?

After all these years of tumultuous change and retail downtime on the "nation's Main Street," the answer is easy. No one, that's who. This great corner, witness to history (as we like to call our quadrennial parades), has in recent years become a place where, at dusk, one would encounter nothing more striking than a few home-scurrying lawyers or confused families from out of town. Where's the Metro, the Hard Rock Cafe, the Harrington Hotel?

Even longtime, long-term Avenue optimists, such as I, could in no way predict Norris Blanks, a middle-aged Australian capitalist with a one-world vision and, obviously, a taste for taking a chance. Blanks came to Washington two years ago and set up his entrepreneurial shop in an office near the National Theatre, observing daily the progress of the pretentious renovation of the modest postwar office building at 13th and Pennsylvania.

To say that he was swept away by the potentialities of the site seems but slight exaggeration. "Washington has a particular destiny in time," he enthuses. "It's becoming a world city as we move into the global community that's coming." In Sydney, besides work "in development and financing," he ran a bookstore with his former wife and supported noncommercial, "consciousness-altering" writers. "I think maybe being new here I'm very respectful of the street with the White House at one end and the Capitol at the other," he says of the avenue's ceremonial stretch. "In a sense we owed the street."

Hence Astraea, a bookstore that's intended as more than a bookstore -- it's part new age emporium (20 percent of its stock is in categories such as Life Force/Energetics), part cafe, part performance space, part art film haven, part library, part study hall and part laid-back "international cultural meeting place," as Blanks describes it.

"People will come in here at all hours to write papers or grade them," says Bronwyn Halliday, one of two managers. "We have a regular who is writing his PhD thesis for the University of Chicago at one of the tables. There's a group that comes in the middle of the night with a guitar and chess sets. A poet can do a reading here at 3 a.m."

The interior architecture has quite a bit to do with the relaxed mood of the space. Blanks, though inclined in conversation to employ "the royal 'we,' " as Halliday observes, apparently deserves most of the credit. "It was such a piecemeal process," Blanks says, "we decided it didn't make sense to hire a professional designer. You have a feeling, something you want to do but can't put into words."

Blanks picked the shelves and fixtures and designed some of them, such as the three chandeliers in the form of cones made of copper strips, each enclosing a dangling, encyclopedia-size lump of rock crystal. Such idiosyncratic touches, derived from Blanks's belief in pyramid energy fields and such, simply give the place a comfortably homemade, unpredictable feel -- it doesn't seem all that new (though it opened on July 15), nor all that artfully designed. Blanks also left the ductwork exposed up on those 14-foot ceilings.

More important are the ampleness of the space -- it encompasses a risky 6,000 square feet -- and its unusually effective layout. The store is roomy enough to accommodate stacks for more than 30,000 books, a "human potential" alcove (still to come, whatever it may be), a tight little office, a small cafe-bar (wine license pending), a couple of good-sized working tables and movable chairs tucked here and there.

Most of the bookcases are free-standing, four-sided affairs about five feet high, arranged in a radiating grid, although tall stacks are appropriately jammed against the walls. Close to two walls are high partitions (one doubling as stacks) arranged in an L-pattern, each with ample openings. These partitions create quiet, private, longitudinal spaces of a kind one would more commonly find in an open-stack library. Like all good bookstores, this one welcomes serious readers and weary browsers, but it provides more facilities than most.

The centerpiece of the floor plan, though it actually is located somewhat off center, is a circular void, a flexible performance space that is put to use most nights for programmed events such as screenings of art films (usual starting time 11 p.m., ticket required for each of the 60 folding chairs) or for unprogrammed performances and gatherings. According to Halliday, theatergoers fresh from "Les Miz" at the National are beginning to wander in, as are patrons of Smithsonian Resident Associates programs on the Mall.

In three dimensions this circle is an ungainly though attractive affair. Consisting of partitions with spacious entryways (which can be closed with folding doors), and capped by a deep suspended ceiling of open metal struts, it looks something like a cross between Stonehenge (Blanks's metaphor) and a rickety starship. This quirky look is mostly accidental, Blanks admits -- his notion was to cover the cap like a canister but he liked the strut work so much he let it be.

And, incidentally, the back-lit band of cherry red plastic that wraps this cylinder at frieze level gives the store an eerie inner glow when seen from Pennsylvania Avenue at night, a nice effect, also serendipitous. It's like a sign without words. (However, the store clearly needs a legible sign too. From a distance it retains a closed-showroom look.)

It was Blanks's intention to invest this space with metaphysical meaning and, possibly, he did -- that's a call that depends on a person's habit of mind. What he certifiably has done throughout the store is to create an identifiable personality and, building outward from the basic geometrical form of the circle, to establish a sense of place. As flexible as it is, this is no homogeneous space; rather, it forms an odd, succinct, pleasant image. It's not slick but in its way it's memorable -- no mean achievement.

Ah, but will it sell? This is the question well-wishers and cynics alike are bound to ask, and to answer with another question: Who knows? "We're, what's the word, 'covering our nut,' " Blanks says with amiable vagueness. This is not an entrepreneur with limited imagination or ambition -- the ideal, he says, would be to create a worldwide chain of seven Astraeas (next stop, Berlin) linked by satellite communication. "I think we're living in a 24-hour world," he says.

Astraea was a Greek goddess of justice, innocence and purity, according to one book, and harmony, tranquillity and wisdom as well, say Blanks and Halliday. In this commercial incarnation she's certainly a fresh idea, not cut from the predictable mold of today's retail industry. The store is exactly the type pined for in the new downtown. "These doors will never close," reads the lettering on them. Quite a thought.