Rushing to work or home, from one appointment to the next, riders scurry past mysterious doors that lead nowhere, walled off platforms and stairwells, faded sections of tile and other odd artifacts of history without a second glance.

But this being the subway's centennial year, Joseph Brennan and Joseph Cunningham, a pair of transit buffs, agreed the other day to lead a small band in search of the original 1904 subway.

Mr. Brennan, 52, helps administer the e-mail system at Columbia University but has never outgrown his childhood fascination with trains. A few years ago, he put together a Web site on the city's abandoned subway stations. Mr. Cunningham, 52, has written several books on the subway. On weekends, he volunteers as a tour guide for the New York City Transit Museum.

The city's subway system first opened as a single line on Oct. 27, 1904. It began at City Hall and ranged north to Grand Central, where it made an abrupt turn west to a sleepy area that had recently been renamed Times Square, before finally heading north again to 145th Street.

The original City Hall station was the system's centerpiece, with vaulted ceilings, skylights and chandeliers. But it closed in 1945. So, the hunt for the 1904 subway begins aboveground. Gesturing at the empty plaza, Mr. Brennan explains how the original line swung out from Brooklyn Bridge station and looped around in front of the steps of City Hall.

And down in the Brooklyn Bridge station, at the southernmost end of the downtown platform for the No. 6 train, Mr. Brennan and Mr. Cunningham point into the gloom, where the tracks disappear around a sharp bend. City Hall station is just around the corner.

A short distance up the platform, he ducks down to peer into a control room across the tracks. Through the glass window, the outline of a staircase is etched on the far wall, like fossilized remains in a cave. There used to be side platforms in this station, for passengers to unload out the rear of the train, Mr. Cunningham says.

Upstairs in the mezzanine, the two men stop in front of a 50-foot section of wall of yellowing tile and red brick wainscoting, by the exit to Brooklyn Bridge. The station was renovated once in the early 1960's and again in the 1990's. But this length of original wall survived.

"It's the one place they didn't touch," Mr. Brennan says.

The group heads next for Bleecker Street. Along the way, the train rattles past the Worth Street station, closed in 1962, one of four now abandoned stations that were part of the original line. Bleecker Street is rare among the original stations because all eight of its medallion-style plates have survived. Walking north, the original white tile walls, with red wainscoting, give way abruptly to a two-tone green, marking an extension made in the early 1960's. (The original stations all had to be extended at some point because local platforms were only 225 feet long and express platforms 350 feet, whereas the modern standard is 525 feet.)

"There was no attempt to blend here," Mr. Brennan says.

For the next stop, they skip Astor Place, a favorite among subway historians for the decorative terra-cotta beaver plaques. But Mr. Cunningham is dismissive: "Everyone knows about the beavers."

Instead, they head to Union Square, where they climb the platform stairs to the passageway connecting the Lexington Avenue line to the N, R, Q and W trains. Here, the Metropolitan Transportation Authority has actually made an effort to preserve its history. Like sentinels, six jagged columns of concrete and tile line the busy passageway. They are remnants of the original two-story walls that used to extend from the platforms. At the tops of these walls, bronze-colored eagles, clutching crests bearing the number "14," looked down on the tracks. For decades, these columns were hidden behind an area used for storage, Mr. Cunningham says. But in the late 1990's, when workers knocked out the walls to create the new passageway in the mezzanine, the columns were left on display, with the crests now at eye-level.

At 23rd Street, the group surfaces briefly to head over to the downtown side. Over by a bus map, an original green tile mosaic has survived.

The two men press on to Grand Central, weaving their way to the platform for the shuttle to Times Square. The original 1904 subway line headed north on Park Avenue and then curved left to enter Grand Central at 42nd Street near Madison Avenue.

Grand Central was an express station, with two local and two express tracks. But one of the downtown express tracks was covered up in 1918, when the Lexington Avenue line was extended north. The original Grand Central station was converted into a shuttle station.

Entering the shuttle area, the track on the far left, Track 1 for the shuttle, is the only one of the three that extends through the station today like the original line did. The track bends south, eventually connecting further down in the tunnel to the downtown tracks near 39th Street.

Over in Times Square, plenty of 1904 remnants can be found. Back then, the area above the subway station had just been renamed, after The New York Times built its new headquarters there. At the shuttle platform, above a map of Midtown, the outline of an archway can be seen under a thick coat of brown paint. It marks the old entrance to the Times building.

Up at 59th Street/Columbus Circle, Mr. Cunningham and Mr. Brennan are interested in only a portion of the station, because much of it was gutted in the 1930's to accommodate a passageway to the Eighth Avenue line.

"Check out the ceiling," Mr. Cunningham says, stopping about 75 feet south of the turnstiles on the uptown side.

Protected by a wooden newsstand that went into the station shortly after it opened and was only removed in the 1980's, a large swath of peeling beige-painted ceiling has been preserved. Intricate rosettes stud supporting beams and encircle light fixtures.

At 66th Street/Lincoln Center, Mr. Cunningham says, "Here we have the old-old and the new-old." In a renovation in the late 1990's, workers installed new station plaques, done in the original 1904 style, but the "LC," woven into the "66," give them away. Lincoln Center did not exist in 1904, Mr. Cunningham says.