The stairs are narrow and gloomy.

Paint peels in vivid chips of blue and green. Windows are slathered with swirls of aqua and magenta paint. Floors threaten to drop away into bottomless darkness. Passages lead to warrens of small rooms filled with oddments, tattered fabric, slivers of things not quite recognizable. There's a whiff of cedar in the air.

That's the interior of Hawthorne Hall, an ornate, late-19th-century landmark that has been empty for years, slowly decaying on Lancaster Avenue near Hamilton Street.

But the past of this building is anything but empty. Behind its arcing brick facade, a hall that once housed meetings of such secret societies as the Knights of Pythias quietly waits the rise of a new secret gathering.

The art collective Rabid Hands, a group based in Brooklyn, New Orleans, and Detroit, has spent weeks inside Hawthorne Hall, conjuring a magical transformation that will acknowledge its unique past and introduce visitors to real and imagined secrets as part of the second Hidden City Festival, which began Thursday at nine sites throughout the city. The festival's projects will run through June 30.

Hidden City links artists to out-of-the-way historic structures, drawing visitors to places they would not ordinarily have a chance to experience.

Within Hawthorne Hall, Rabid Hands is concocting its own secret Society of Pythagoras, with an initiation room, a banquet hall, oaths, performances, light-and-sound environments, and mysterious rooms filled with the primally charged elements of the society.

One recent day, collective member Vanessa Cronan was constructing a "transmission tower" that angled out of a large, previously hidden space below the auditorium.

"This transmission tower fell through the ceiling and is sinking into the floor," she said, looking at a triangular form that was, indeed, sinking into the floor. "It pierced the underworld, and messages started filtering up. They represent another frequency of consciousness that exists in the earth, where the roots grow."

Visitors will pass through this room to wander through two floors that are gradually taking on the look of The Cabinet of Dr. Caligari, a surreal 1920 film exploring the bizarre world of Cesare, the somnambulist.

The first Hidden City Festival, in 2009, drew about 10,000 visitors to nine sites ranging from the old Disston Saw Works in Tacony to North Broad Street's Metropolitan Opera House to Shiloh Baptist Church in South Philadelphia.

Thaddeus Squire, Hidden City's founder, and founder and managing director of CultureWorks Greater Philadelphia, said this year's festival is less curated; instead, sites were suggested, a call for proposals went out to artists, and community input was sought. Though less top-down this time, the goal is the same: to highlight abandoned or underused sites off the well-trod path of historic Philadelphia.

Shivtei Yeshuron-Ezras Israel, a storefront synagogue at 2015 S. Fourth St. in use since the early 20th century, will serve as home to textile designer Andrew Dahlgren. He will install modern knitting equipment on the second floor and invite visitors to watch and assist in creating a vast "sweater" that will cover the building facade. This benign, domesticated project, intended in part to evoke the crushing past of small immigrant sweatshops, will be augmented at the site by a concert of John Zorn's Book of Angels, presented by Ars Nova Workshop.

Fort Mifflin and Mud Island will serve as the site for artists Ben Neiditz and Zach Webber to create Ruins at High Battery, a series of shore structures built from scavenged materials, evoking transient, early river shanties, among other things.

At the Athenaeum, 216 S. Sixth St., artist Ruth Scott Blackson will use Edgar Allan Poe as inspiration to create an artist book suggested by Poe's use of the Athenaeum library during his time in Philadelphia in the 1830s. At the historic John Grass Wood Turning Co., founded in 1863 at 146 N. Second St., the Center for Art in Wood and artisan Joe McTeague will, of course, turn some wood.

At the old swimming pool at the Fairmount Water Works - the so-called Kelly Natatorium, closed for decades - the artist collective Camp Little Hope will create a kind of pop-up cafe, serving visitors tea, perhaps some sympathy, and maybe a little understanding of the human impact on the water supply.

Other projects: Philadelphia artists Billy and Steven Dufala's Oil & Water, an installation at the Globe Dye Works, 4500 Worth St. in Frankford; Data Garden's sound installation at the Historical Society of Frankford, 1507 Orthodox St.

Oakland, Calif.-based artist Jacob Wick is leading the occupation of Germantown Town Hall - finished in 1923 for a "town" that was part of a city and that never used it as such. It is being transformed into the City Hall for Free Germantown, where community-based activities, performances, meetings, and events will take place all month.

Hidden City, Revealed

For information on events, performances, talks, ticketing, and times,

visit the Hidden City Festival website, Call the box office at 267-428-0575.