Proportion—the relationship of parts to wholes—only makes architectural sense when it’s joined to scale, the actual dimension of things. For millennia, from Vitruvius to Leonardo to Le Corbusier, an idealized body has been used to make this connection. Hence the commonplace phrase “human scale,” merging aesthetic and practical desires. These are clearly revealed in forms and feelings at the extremity, like the half-height floor in Being John Malkovich, too tiny to stand up in, or Albert Speer’s Volkshalle, big enough to hold an army and generate its own weather.

That the sweet spot in human scale isn’t fixed suggests that spaces have to be socially and psychically proportionate, whether to conduce feelings of cozy domesticity or to induce shock and awe. The churches built by the conquistadors were meant to dazzle the natives into docility, much as the great European cathedrals embodied the mightiness of the divinity and the smallness of its subjects, dwarfed by vaulted ceilings reaching to the heavens. This capability isn’t always negative; it can also celebrate and inspire with grandeur, loftiness, and numinous space without end. Chartres is indisputably fabulous, and without it culture would be bereft. But while it may be wonderful as an architectural absolute—much as the pyramids were to their age or the interstates to our own—a Gothic cathedral’s utility is limited by its relative unsuitability for secular purposes. We would not instinctively think to build one for, shall we say, the entrance to a local stop on the IRT. Or would we?

In Flaubert’s Dictionary of Received Ideas, the entry for “railway stations” states: “Always go into ecstasies about them: cite them as models of architecture.” With the completion of Santiago Calatrava’s Oculus—that remarkable creature at the World Trade Center that’s effectively an entrance pavilion for the PATH train to New Jersey and several subway lines—the utility/expression chestnut is set for a thorough roasting. Finally open after a decade of construction and the expenditure of nearly $4 billion (including $655 million for “administrative costs”), the Oculus is at once incredible and infuriating. It’s a black hole for bucks, a stunningly autonomous monument, and a medium of creative displacement—a vortex that has absorbed the imaginative energy that might have been expended on its surroundings (the vanishing Ground Zero arts center or those mediocre office towers) or elsewhere (a new Penn Station and Port Authority Bus Terminal, the renovation of who knows how many subway platforms, or the desperately needed renewal of the system’s creaky, century-old technical infrastructure and frail capacity). The Oculus struggles to symbolize both the purity of its strictly artistic utility (which is to say, its lordly functional superfluity) and something more ineffable still.

Calatrava has produced a building that is singular but not recondite, a train station and a cathedral. It’s a glistening white steel rib cage, 160 feet high and 392 feet long, enclosing a nave-like space with a volume greater than Grand Central Terminal’s main concourse and a distinctive surmounting crown. Dense rows of vertical ribs alternate with lofty glass to envelop the great room and then turn outward to become gigantic spikes— pituitary versions of those radiating from the Statue of Liberty’s crown—that sprout from the building like enormous porcupine quills or the bones of a pterodactyl’s wings. The mixed metaphor—it’s a bird! It’s a plane! A phoenix! A stegosaurus!—speaks to the irresistibly biomorphic character of the building and its formal originality. It is a real rara avis, albeit one with a strong family resemblance to other members of the Calatrava bestiary.

The Oculus sits at a canny remove from scenes of both spirituality and mass movement, at once neutralizing and absorbing their purposiveness. The 9/11 memorial pits and a new Greek Orthodox church (also designed by Calatrava) are not simply across or down the street but inaccessible from within its gleaming lantern. This arm’s-length distance makes the Oculus’s spirituality pagan: It occupies the space initially meant to have been evanescently illuminated by Daniel Libeskind’s “Wedge of Light,” a marker of time offered as an equivalent to Abu Simbel or Stonehenge, but trivialized by the banality of the erstwhile framing and enabling office-tower architecture that limned its solar slot. Likewise, the Oculus isn’t exactly a train station, but rather a centroid that organizes pathways to a series of more autonomous stations at varying distances and relations—a distributed aggregation of tracks that may rival Penn Station’s but, individually, are miniatures in relation to the huge space. Much of the power of the Oculus comes from this disproportion: the enormous and beautiful uncolumned space that shelters the little stairways down to the PATH’s five tracks, with the Broadway local crossing overhead in a massive tube supported by monster trusses.

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Let’s set aside the build-one-battleship-or-10,000-schools argument that’s been at the heart of virtually everything written about the structure to date: That argument is both conclusive and concluded. Instead, let’s consider the poetics of the Oculus’s assembly and tectonics. I really like the big beast as both object and space, and already feel sad about its imminent squishing between the two crappy towers that will flank it. If only it could just walk—or fly—away! Indeed, Calatrava had originally wanted its wings to flap, and I sympathize with his disappointment that this motility was value-engineered into stasis.

Calatrava is both beloved and reviled for the anatomical literalism of so much of his work: the balance, joinery, rigidity, and rhythm of the skeletal. Because the Oculus is so expressively “ornamental”—larded with flourishes, enormous and otherwise, that do nothing but please the eye—it fudges the boundary between architecture and sculpture, prompting some of the same questions raised by that high priest of art-world avoirdupois, Richard Serra. Serra’s work demands to be seen as more than merely sculptural in its modulations of space and passage, and derives much of its power from the threateningly massive heft of all that Cor-Ten steel. As with the Calatrava, much of the impact of Serra’s sculpture has to do with the chest-thumping weight of those Torqued Ellipses and precariously leaning, dangerous walls. But Calatrava and Serra riff differently on functionalism’s asymptotic parsimony: With pieces like Tilted Arc, Serra goes for the massively minimal, whereas Calatrava madly multiplies structural members and coyly conceals and reveals which ones are actually bearing the load.

The very careful—even maniacal—engineering of Calatrava’s designs suggests a crucial difference from Gothic cathedrals. Although they frequently collapsed during, and after, their construction, those churches were far and away the most structurally advanced architecture conceived for a period of close to two millennia, right out there at the edge of the possible. Their height, span, complexity, and lightness were amazing and—given the pure seat-of-the-pants, trial-and-error structural calculation involved—astonishingly daring. Despite its visual and spatial affinities, the Oculus is very different. Calatrava, who trained as both an architect and an engineer, has always stressed the expressive import of structure, most famously in his often magical bridges and stations, works that embody engineering’s highest technical, economic, and artistic aspiration: elegance.

Still, this bird’s a turkey—so expensive, heavy, and dense with structure, and so willing to blur the line between the functional and the decorative, that understanding the prosody of its construction also requires an accounting of its extravagance. The design isn’t simply highly conservative in terms of its relationship to risk (balancing risk and means is the key dialectic of structural performance); it is also flagrantly, expressively profligate in its conservation of materials, an inescapable responsibility in any 21st-century construction. According to Calatrava’s firm, the amount of steel used weighs in at an astonishing 15,250 tons. (For comparison’s sake, a “mere” 50,000 were used to build 1 World Trade Center, the continent’s tallest building.) The distinguished structural engineer Guy Nordenson argues that this gives the Oculus what may effectively be the largest carbon footprint, per unit volume, of any building on the planet. And Donald and Bernie, take note: All that steel comes from Europe!

But let us assume for the moment that there is some virtue in extravagance, and that the Oculus has redeemed the artistic potential squandered at Ground Zero. Let’s further assert that vast expenditure on public works is the hallmark of a great civilization, that the game is not zero-sum—i.e., the savings realized by removing a quill or two would not be applied to a housing project in Brooklyn—and that the thing can be judged artistically sui generis. Still, the time and expense laid out do count in that critical calculus; after all those years and cash, the thing should be close to perfect. Here arrive my reservations: I find the Oculus tremendous and beautiful, but not quite right. I am disturbed that, about two-thirds of the way out on the rows of quills, there’s a steel tube that joins them all together, a stiffener and a spacer. Really? Tens of millions spent on that imported steel and those ribs can’t fly solo? And what about the funky fireproofing that kills the precise angularity of the metal beneath? Or the inaccessible beams and crannies that are sure to turn the now-pristine thing into a permanent museum of dust?

As structure, the Oculus is made like a bridge—even though it doesn’t function as one—and perforce becomes a slightly i­ronic reflection on the techniques of bridge-building. Each of the long sides holds a structural arch, and the huge ribs that appear to support these arches lean in to provide a hybrid of walls and roof before taking, as they pass the line of the arch, a dramatic outward turn to form those sideways-soaring wings or quills—a pure, flamboyant, “superfluous” ornamental expression, despite weighing thousands of structurally challenging tons. However, although the arches are symmetrical, the quills are not: Each side is different, reversing the pattern of the other. This eccentric loading and the variable length of the ribs as they rise to meet the curve of the arches mean that much computer power has been spent on the design of the hidden base: an oval ring embedded at grade that acts as the bottom chord of a giant Vierendeel truss that stiffens those walls against the wind and for self-support.

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The most self-consciously witty aspect of the structure is the continuous, operable glass skylight that runs the length of the building’s ridge line, forming a gap between the two arches (for my money, this should have been left unglazed, like the eponymous oculus in the Pantheon in Rome). These are actually joined, and carried, only at their ends, where they land on massive buttressing knuckles, the push-me/pull-you beastie heads through whose mouths the building is entered at street level. The long sky-lit slit defies the visually induced expectation that the ribs are holding things up and that the two long sides of the building should thus be joined together across this seam to form a series of A-frames—a very sturdy and conventional configuration that would be made stronger still if the arches were linking the row of frames together. The absence of this joinery reveals that the arches really are bearing the load that one assumes is being carried by the ribs. One imagines, too, that the ribs and flying quills are in near equipoise, relieving the expected rotational stress on the ring-base caused by those long cantilevers. Calatrava gives plenty of further hints about the limited role of the ribs by not bringing them down to the lowest level of the building and instead bending them into a rhythmic filigree, a curlicue caesura that seems barely connected to the walls! Here Calatrava plays cheerfully with the line between the fussy and the butch, deliberately marking his system as very different from the compressive clarity of a cathedral’s buttresses, which bulk up progressively as they head earthward and plunge resolutely into the supporting ground.

The Oculus is further distinguished from Chartres by its organization of movement. The main circulatory action in a cathedral is singularly directional: enter at the back of the nave, move toward the altar, pray, reverse. There’s generally a secondary route around the perimeter—lined with shrines, confessionals, fonts, chapels—that can be accessed without traversing the main axis (an array prosaically repeated in the Oculus with a two-tiered ring of shops). Whereas cathedrals—­towers and crypts notwithstanding—are invariably slightly elevated continuations of the ground plane, the primary grade of the Oculus is two levels below the street. The privileged movement plane is subterranean, and the Oculus functions diagrammatically as the head of an octopus, with tentacular extensions radiating to four transit nodes (including the much more concentrated nexus at Fulton Street, its own ambitious dome made ever so sad by the drama down the block) and to the lobbies of surrounding buildings, often over fairly long distances. And unlike a cathedral, for which the ground is a single plane, the multiple levels of this space are inelegantly joined by a plethora of escalators and stairs that look seriously underscaled. This is nowhere more unsatisfying than at the ends of the nave, where entries from ground level lead to klutzy cantilevered escalators that, switching back and forth, are more tease than celebration of the glorious axial view. Many wedding couples will be photographed on the intermediate landing.

I admit to being among those who had argued for a no-build solution at Ground Zero, for turning the entire site into a great space of public assembly—a wanton display of democracy’s greatest physical freedom. My concerns about the partition of commerce and commemoration are not relieved, alas, by the final results. However “spiritual” Calatrava’s astounding building may be, thick demising walls separate without acknowledgment the money-changers from the more literally sacred environment of the adjoining temple: the 9/11 memorial and museum. All those glistening Italian-marble corridors that the Oculus organizes are lined with retail, retail, and more retail, their deluxe white in blinding contrast to the memorial’s somber black. Conceptually, the complex is a glorious reinstatement of exactly what existed there before 9/11: an underground shopping mall brought to us by our old friends at the Westfield Corporation. Step aside, Woolworth Building—­this is the true cathedral of commerce!

And yet… I was able to tour the site a number of times during construction, and the sheer ingenuity of the logistics, as well as the fiendishly complex challenges of dealing with the massive ruin, with trains running across the site without surcease, with an astonishing tangle of infrastructure, with the mammoth 24-hour movement of people and materials, all make this a breathtaking achievement. Perhaps it’s the dedicated workers and engineers—whose labor made this transformation possible, and whose contribution invisibly undergirds all that hypertrophied form rising above the surface—to whom we should truly turn in admiration, gratitude, and celebration.