On Monday, thousands of subway riders getting off trains at Chambers Street in Lower Manhattan will pull open metal-and-glass doors that have been closed for years and stream through a travertine-paved passageway.  Most will be lost in rush-hour oblivion. Some will appreciate the restored shortcut to PATH trains. A few will gasp in recognition.  That mottled, straw-colored travertine will tell them exactly where they are standing: within the last extant remnant of the original World Trade Center, a portion of the concourse that looks just as it did in the 1970s.  Well, not exactly. One door, now encased in protective glass, has been spray-painted with orange markings. The notation “MATF 1” is scribbled on it. Below that, “9 13.” The graffiti let rescue and recovery workers know, after the 2001 terrorist attack, that the area had been searched on Sept. 13 by the Massachusetts Task Force 1 Urban Search and Rescue Team, based in Beverly, Mass., and working for the Federal Emergency Management Agency.  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.  At the moment, the passageway is not useful for disabled riders because it leads to a broad flight of 26 marble stairs down into the hub. Glenn P. Guzi, a program director at the authority, said an elevator will be installed next year.  The passageway will serve riders on the A, C, E, 2 and 3 lines. Before the 2001 attack, about 10,000 people went through it daily, Mr. Plate said.  After the twin towers were destroyed on Sept. 11, 2001, the passageway was closed. It reopened for a few years as a temporary connection between the subway and PATH commuter rail systems, then was closed to permit construction of the hub. During that time, the travertine, handrails and doors were covered in protective plywood.  Handsome directional signs inside the passageway are to be reinstalled. A less-than-handsome overhead sign outside the passageway (“PATH Trains to New Jersey”) will not be coming back.  Neither will WTC Newsstand & Novelties, next to the passageway, which was owned and operated by the brothers Reajul Islam and Fakrul Alam-Onar. In September 2015, Mr. Islam said business had dropped to between $100 and $200 a day, from $2,000 to $3,000 a day when the passageway was in use. The few people who stopped by, he said, limited themselves to bottled water or candy bars.  Mr. Islam said at the time that he needed the passageway to reopen “immediately” if business was to recover. More than a year elapsed. The newsstand straggled along. Then, at the end of November, the brothers surrendered their lease to the Metropolitan Transportation Authority.  A spokesman for the agency said the newsstand would probably be demolished.  A version of this article appears in print on December 19, 2016, on Page A19 of the New York edition with the headline: Subterranean Vestige of Original Trade Center Is Set to Return to Duty. Order Reprints| Today's Paper|Subscribe
A passageway at the Chambers Street subway station, preserved during reconstruction efforts, bears the marks of rescue efforts after the Sept. 11, 2001, attack.