At yesterday’s annual awards luncheon of the American Institute of Architects, David Childs, head of Skidmore, Owings & Merrill, unveiled the final plans for the Freedom Tower at ground zero. In so doing, he greatly fleshed out the project he announced a year ago, when he radically revised the building as first conceived by Daniel Libeskind. Surely one can discern a common thread in both versions, but Mr. Childs’s building is fundamentally different from Mr. Libeskind’s – and the change is for the better.

While Mr. Libeskind’s model was irregularly faceted and somewhat asymmetrical, in keeping with the Deconstructivist style with which he is often associated, this latest version emphatically reasserts its fealty to the conceptual grid. The facets remain in part, but they now behave themselves, gliding with exemplary grace up the four corners of the tower.

The lofty spire that Mr. Childs also inherited from Mr. Libeskind now sits in the center of the observation deck, rather than to the side, as was originally planned. In fact, the only thing that survives intact from Mr. Libeskind’s version is the somewhat irrelevant symbolism according to which the building is to rise 1,776 feet, in commemoration of the year of our nation’s founding.

Mr. Childs made yesterday’s announcement at 7 World Trade Center, which he also designed for the site’s developer, Larry Silverstein. This building, which stands catty-corner to the site destined for the Freedom Tower, bears a certain similarity to the larger building that will soon begin to rise there, pre-eminently in the way its pale glass skin emerges from a fortified concrete base that is set in a graceful public plaza. Although 7 World Trade Center was widely disparaged by architectural critics (not least by yours truly) when its plans first appeared more than three years ago, it has turned out quite well.

The dominant idea in the new conception of the Freedom Tower is to create a building that is both as solid as possible and, in appearance at least, as immaterial as possible. Clad in a skin of translucent, prismatic glass that sparkles in the sun, it will rise from a concrete base whose dimensions and distance from the street were determined by safety considerations, in consultation with the Police Department.

Visitors will gain access to the building by mounting what, by contemporary New York standards, is an imposing sequence of steps. These lead up to a platform whose trees and waterworks will be designed by Peter Walker, who is collaborating with Michael Arad on the memorial that will stand across the street, to the south of the completed tower.

The best thing about the base looks to be the four massive portals, one on each side, that punctuate the monolithic expanse of prismatic glass. There is something that one might call neo-Babylonian about these entrances: They seek the kind of grandeur that has largely vanished from the diapason of both modern and postmodern architecture. Contemporary buildings are often big, but almost never grand.

From the base, the shaft will rise in a sequence of floor-to-ceiling glass plates that were not available, apparently, in the construction of 7 World Trade Center; by eliminating the intermediate spandrels, these will produce an even more sheer effect than is evident in the earlier building.

Mr. Childs also published renderings of the lobby and the underground concourse. Presumably these are the parts of the design that are most liable to change as things progress. That is a good thing, since they appear to be somewhat lackluster, more in keeping with the corporate mystique that has defined the house style of Skidmore, Owings & Merrill for the past half-century.

Although Mr. Childs has done a good job of concealing, or at least downplaying, the safety concerns that were so determinative a factor in the evolution of his design, one cannot help but be acutely aware of their presence, whether in the concrete base or in the recession from the street or the minimalist bollards, shaped like a phalanx of squat dominoes, that surround the building.

In a vastly uncertain world, one can never claim to be certain of anything. Yet I would hazard the guess that none of these expedients will ever be needed. Rather, like the moats and machicolations of medieval fortifications, they seek to parry a menace that will recede ever further from the concerns of living men and women. And in the process they will acquire a period interest and a visual charm. As to the latter, they are, to judge from these latest renderings, already well on their way.