Commuters can once again walk beneath the World Trade Center site in an area that's been closed since 9/11.

The 600-foot-long, marble-paved passageway will accommodate mass-transit users going into and out of lower Manhattan.

The concourse will also eventually feature retail outlets.

The Port Authority of New York and New Jersey says the passageway replaces a critical transit connection that was lost in the terrorist attacks on Sept. 11, 2001.

The underground passageway runs west from the PATH station and underneath West Street. Pedestrians had been crossing the busy roadway or using a pedestrian bridge that's being dismantled.

The passageway is part of a nearly $4 billion redevelopment of the World Trade Center site that includes a new transportation hub scheduled to be completed in 2015.

A ribbon-cutting was held Thursday.