If you've been curious how to get yourself into a few of Philadelphia's landmarks that have always seemed daunting to approach, if not virtually inaccessible, help has arrived.

Hidden City Philadelphia, a new arts festival that debuted last weekend, has made almost all things possible this month. On its to-do list for exhibitions (dance and music performances are taking place at various sites as well) are Founder's Hall at Girard College, Mother Bethel AME Church, Disston Saw Works, Shiloh Baptist Church, and the German Society of Pennsylvania.

But hurry to the Web site, www.hiddencityphila.org - these exhibitions are open to the public only on weekends through June 28.

Been to Tacony, or to a historic but still-active saw works lately? I hadn't, so I decided to visit the historic Northeast Philadelphia neighborhood and its oldest and best-known Industrial Age survivor, Disston Saw Works, to see "Running True," a sound, film, and sculpture installation by Philadelphia artists John Phillips and Carolyn Healy.

Phillips and Healy, husband and wife and frequent collaborators, have transformed the crepuscular interior of one of Disston's factory buildings into a virtuoso multimedia environment replete with film projections of present-day Disston employees at work; the sounds of saw manufacturing; eerie lighting (much of the space is enveloped in darkness, all the better to see the films), and arrangements of objects, ancient ledger books, and blueprints gleaned from the saw works' large property on the Delaware River.

Phillips and Healy's cleverly calibrated synchronization of sound, image, and object offers a remarkable interpretation of the site's history and is the perfect realization of what Hidden City Philadelphia set out to achieve.

Having seen the first two floors of Founder's Hall, the main and oldest building at Girard College, which was designed by Thomas U. Walter and erected between 1833 and 1847, I had eyed the roped-off staircase to the third floor before, wondering how I could sneak upstairs. If any ghosts were drifting through this building, they surely were residing up there.

Clearly, Steve Roden found the ghosts of Founder's Hall when he visited the third floor for the first time. His resulting three-part installation, "nothing but what is therein contained," is a communion with the spirits of Walter, philanthropist shipping merchant Stephen Girard, and some of the students of Girard College whose classes were held in these spectacular domed rooms. (Walter, a Philadelphian who went on to be one of the architects of the U.S. Capitol, designed that building's central dome.)

The first of these enormous rooms, which recently was painted white, has a single table in it on which Roden has displayed his letterpress book, "the glassychord" (Ben Franklin's original name for his glass armonica), in which he has assembled a pastiche of quotations from prominent Philadelphians who were alive during construction of Founder's Hall.

In the second room, which, like the third, has peeling walls and the appearance of having been shut off from the rest of the building for decades, Roden has arranged 17 simple wood boxes to look as if they were left there years ago to gather dust. Each is stenciled with the name of one of Girard's ships. Against them, Roden has propped framed colored-pencil drawings that appear to be abstract but are loosely based on early drawings of Girard College and its environs.

The third room is empty except for a tall sculpture at its center constructed from long wooden sticks held together with wire and stained the colors of wooden toys: bright yellow, red, blue, green, violet. Its extenuated geometry brings to mind dunce caps, intersecting stars, an Amish barn-raising gone awry.

The sound track in this room is particularly haunting - a tinging sound, possibly produced by a triangle, that's reminiscent of old-fashioned children's songs and Gregorian chant. I felt a sudden cold breeze brush against my arm, even though the room was as still as a tomb.

Disston Saw Works, 6795 State Rd., 11 a.m. to 7 p.m. Saturdays, 1 to 7 p.m. Sundays. Founder's Hall, Girard College, 2101 S. College Ave., 11 a.m. to 7 p.m. Saturdays and Sundays. www.hiddencityphila.org. 267-597-3808. Through June 28.