The Office of Public Art has always sought to illuminate the art we don't notice in our everyday lives, but its newest guided walking tour takes that literally by examining public art that experiments with light.

Tomorrow's Art Experiments with Light: Downtown Walking Tour covers four works — "Rivers of Light," "168 Lightbulbs," "The Puddler" and "Mix-n-Match."

"Rivers of Light," Jane Haskell's 1984 creation in painted aluminum, neon and glass block, sits inside the Steel Plaza T station at the platform level. The 5,000 square-foot environment plays with splashes of color — including warm hues in the morning and cool shades after dusk — to create the illusion of dancing river waters.

Above the entrance to Wood Street Gallery, Jim Campbell's 2001 piece "168 Lightbulbs" displays differing images using alternating light from (yep) 168 bulbs. Some of the representations include people crossing the street, traffic and even the image of Claude Shannon, the father of information technology.

"The Puddler," a work of stained glass built into the facade the 300 Sixth Avenue Building, is more of an urban mystery. While the piece was fabricated by Harriton Carved Glass Company, in 1939, the artist is unknown. The mural depicts a figure puddling steel — or placing iron into a hot furnace then stirring it. The piece is lit up at night and features animated sparks from the hot metal, a tribute to the Steel City.

The newest contribution to Pittsburgh light art, "Mix-n-Match," is the brainchild of Dutch artist Allard van Hoorn. The installation involves a series of LED bulbs laid out in the form of an oversized record-player that light up in tandem with audio tracks incorporating sounds recorded with groups of local residents. (The groups include Downtown street-cleaners and Point Park tap-dance students.) It was incorporated into the heart of Market Square last Friday.

The Office of Public Art's Rachel Klipa will lead the bilingual tour — presented in both English and Spanish.

Art Experiments with Light: Downtown Walking Tour is presented in collaboration with the Office of Public Art, Welcoming Pittsburgh and Café con Leche.

Tickets are $8 in advance and $10 at the door. The tour begins at 7 p.m. tomorrow at the Steel Plaza T station, platform level.

Call 412-391-2060 or visit www.publicartpittsburgh.org to register.