The final designs for Towers Two, Three and Four at the World Trade Center site were unveiled at the 7 World Trade Center Thursday, less than one week before the sixth anniversary of the September 11th attacks.

Developer Larry Silverstein and a group of architects unveiled the final, updated designs for the three buildings, which are scheduled to begin construction in January.

"From a design perspective, each of the three towers is distinct. Yet all three are architecturally compatible and work together seamlessly,” said Silverstein.

The changes build upon the conceptual designs unveiled last year and provide greater detail on design elements including lobbies, public space, and building exteriors. He said the buildings will be environmentally friendly and will use the latest technology and safety innovations.

Silverstein acknowledged that the project has met with many setbacks over the years, but he says progress is finally being made.

“It is a testament to the genius and the shared mission of all involved that we have reached this point," he said.

"Along the way, we've had our stumbling blocks, including the recent Deutsche Bank catastrophe,” said Assembly Speaker Sheldon Silver. “But we have a stronger and more dedicated leadership team now."

"Today that project behind us is really firing on all cylinders,” said Port Authority Executive Director Anthony Shorris. “Six hundred plus construction workers are there on the site every day, hundreds of pieces of heavy equipment on the site. $1.8 billion of construction contracts have actually already been already awarded by the Port Authority. And as a result, at last, we're seeing real progress on every element of the site."

The Freedom Tower is the signature skyscraper, standing 1,776 feet on the northwest part of the site. The base is under construction. The frame will reach ground level next year, to be complete by 2011.

Towers Three and Four, which will rise to 71 stories and 64 stories at sit at 175 and 150 Greenwich Street, respectively, are set to be completed in 2012.

Tower Two, at 200 Greenwich Street, will be built 79 stories tall and is set for completion in 2013.

When the project — which will occupy nearly 16 acres of Lower Manhattan — is complete, there will be millions of square feet of office space and a half a million square feet of retail space. The total price tag for rebuilding the site could be around $16-$17 billion.

“This is an exciting time and we have before us a rare opportunity to make a lasting contribution to New York City,” said Silverstein.

The Port Authority says it will not clip the wings of the proposed transit hub at the World Trade Center site. The roof, which will be in the shape of a pair of wings, will be able to open and close to admit light into the main floor.

Engineers had been looking into ways to reduce rising costs on the project. The Port Authority says the changes instead will be mostly in the subterranean structures rather than the terminal or roof.

The $2-billion transit hub, designed by renowned architect Santiago Calatrava, will be ready at the end of 2009. Work on the foundation is under way and construction of the platform will begin next year.

The architects also provided an update on plans for the September 11th memorial slated for the site.

The project's name recently changed to the "National September 11th Memorial and Museum at the World Trade Center." An aboveground plaza is expected to open in 2009 and the museum a year later.

Two of the World Trade Center's tridents, which remained standing after the attacks, will greet visitors as they enter the memorial.

The capital campaign — led by Mayor Michael Bloomberg — has raised more than $300 million this year.

“It's big corporate gifts. It's $5 from a class in South Carolina,” said National September 11 Memorial & Museum President Joe Daniels.

A key plan to take the memorial on a cross-country fundraising tour is moving forward as well. The tour begins Monday, one day before the sixth anniversary of the attacks, in Colombia, South Carolina and then moves on to 15 other cities.