The image of a bird in flight is not one normally associated with an underground transportation center, but architect Santiago Calatrava has perfectly managed to marry the two. As designed, the World Trade Center (WTC) transportation hub -- built with two 150-feet-tall canopies extending from a glass- and steel-ribbed “body” -- sits at street level like a bird poised for flight, delivering natural light to the PATH train platform 60 feet below ground.

Click here to view a slide show featuring the latest renderings of this project. Also view animations showing an exterior view and interior view of the transportation hub.

Calatrava originally unveiled his design to the public in early 2004 and revised it in July 2005 to address security, engineering, and feasibility elements for the landmark structure.

The $2 billion hub will sit at the northeast corner of the WTC site at Church and Vesey Streets and is expected to form an underground connection between the World Financial Center and the Metropolitan Transportation Authority’s Fulton Street Transit Center. Through it, pedestrians will have access to Hudson River ferry terminals, PATH trains, 13 subway lines, and, potentially, a direct rail link to JFK International Airport.

Calatrava’s reworked plan will reduce the amount of glass between the canopy’s steel “ribs,” while the total number of ribs will be doubled. The main hall itself will be shortened from 360 to 330 feet, further from the curb line of Church Street.

Inside the station, Calatrava designed the underground concourse, mezzanine, and platform levels to be free of vertical columns for a greater sense of light, movement, and openness. This feeling of openness will be further magnified by a retractable ceiling -- an architectural feature most common to sports arenas -- planned for use on sunny days and annually on September 11. As part of Calatrava’s revisions, the ceiling will open to 30 feet wide, instead of the original 45 feet.

“The building is built with steel, glass, and light. They will all be equal building materials,” Calatrava said. “The light will arrive at the platform, and visitors will feel like they are arriving in a great place, a welcoming place.”

Calatrava said that Daniel Libeskind’s original master plan both guided his design and served as inspiration, stating that the transportation hub “articulates with Libeskind’s beautiful plan. The station fits like a centerpiece in the middle of the plaza.”

The hub in its entirety, which is being funded by the Federal Transit Administration, should open by late 2009 and is expected to eventually serve more than 250,000 travelers daily.

For more information about the temporary PATH station now open to the public, please click here or visit the Port Authority's website at www.pathrestoration.com.

Images courtesy of the Port Authority of New York and New Jersey.