As the first building scheduled to go up at Ground Zero, the Freedom Tower offers a glimpse into the future of the site as a whole, and whether it will work as an urban area. The tower is an impressive building, one that combines Daniel Libeskind's vision with David Childs' innovative use of structure. Childs' use of cables that enclose windmills over a thousand feet in the air, for example, will help create a building that can become a symbol of New York City. But Freedom Tower is not a complete success. It must be brought more closely in line with what Libeskind originally proposed.

Libeskind envisioned a tower that was thin and graceful, with a sloped roof and a spire that mirrored the arm of the Statue of Liberty. While Childs' earlier designs violated this vision by making a bulky, twisting tower much larger than Libeskind wanted, the recently released plan brings it more closely in line with Libeskind's concept, cutting the height of the building back down, for example, to 1,776 feet.

But Libeskind intended the spire to be something that soared like the arm of the Statue of Liberty, starting at the base of the building and running up all the way through it. It was an integral part of the building's form. To me, the spire that Childs has designed looks like a dunce cap, an appendage simply slapped onto the edge of the roof

It would not be too difficult to take the top third of the building, the 30-story skeletal form that includes the windmills, and shape it so that the spire really becomes part of the building architecturally.

Most importantly, for the World Trade Center site to be a successful urban design, all the buildings must work together to create a whole. That is why Rockefeller Center works so well. Its buildings are a family that relate to each other as part of a whole; there is a design consistency that creates the ensemble. You look at any building in the project and you say "That is Rockefeller Center."

If we want people to go to Ground Zero and say "That is the World Trade Center," we need to adhere to the design principles developed for the overall site. Such coherence is how great spaces are made. Without it, you risk chaos.

Yet Childs appears to be disregarding Libeskind's master concept for the site. I couldn't help but notice that in the model that accompanied the new design for Freedom Tower, the shorter buildings on the site have really been bulked up, apparently abandoning Libeskind's vision.

If true, this would be disappointing. Childs has done some impressive things with his design. But as admirable as some of these innovations are, unless they are molded into a bigger and grander concept -- Libeskind's concept -- they will fall flat.

Beverly Willis, an architect, is the co-chair of Rebuild Downtown Our Town. This article was adapted from an interview.