It is an astonishing time capsule, linking the muscular, hard-edge New York subway with the voluptuous, snow-white world that the architect Santiago Calatrava conjured in the World Trade Center Transportation Hub.

“Our theme is respecting and remembering the past, and including it in a sophisticated way,” said Steven Plate, the chief of major capital projects at the Port Authority of New York and New Jersey, which restored the passageway as part of the $4 billion transportation hub and shopping mall.

Under Section 106 of the National Historic Preservation Act, the authority was required, as a condition of receiving federal financing for the hub, to salvage, preserve or document remnants and artifacts of the trade center. This includes what is called the “E Subway Entrance,” since the passageway leads to and from the Chambers Street terminus on the E line.

The authority agreed to incorporate original elements of the passageway — travertine flooring, handrails, steps and ramp, doors and overhead signs — into the new transportation hub. Explanatory signs have been placed on the walls of the passageway and on the door with the “MATF 1” marking.