It's a 25-foot-tall, 2,000-square-foot high-definition LED screen which at times mimics the wood-paneled wall of the main lobby of the Comcast Center, which opened in June.
Mostly by word of mouth, the enormous video installation has been drawing a growing stream of visitors to the 975-foot tower, which owner Liberty Property Trust is hoping will become a destination a la New York's Rockefeller Center.
"We are stunned by the reaction we have gotten," said D'Arcy Rudnay, senior vice president for corporate communications at Comcast, headquartered in the building.
City tourism officials said they added the Comcast Center to their Web site, gophila.com, after both residents and tourists began asking for more information about the attraction.
"I'm sure those people will say, 'OK, I have to do the (Liberty) Bell, Independence Hall, cheesesteaks, the Rocky statue and the Comcast screen,"' said Meryl Levitz, chief executive of the Greater Philadelphia Tourism Marketing Corp.
The video wall has thousands of hours of content to offer at five times the resolution of a typical HD television, from dance routines to vistas of outer space.
Much of the content is Philly-centric, with panoramic views of the city's historical sites. And then there are NASA satellite images of Earth and dancers flying across the screen on giant pencils.
Images of cranes and metal machinery randomly drop down to form a clock whose hands whiz around and gently stop on the correct time - typically prompting lobby visitors to check their own watches.
Liberty Property Trust and Comcast said they wanted the skyscraper to not just change Philadelphia's skyline but also to offer visitors something high-tech - and artsy - in return.
They contracted David Niles and his production engineering company, Niles Creative Group, to design the screen and provide ever-changing content.
Niles, who can sit in his New York-based den and watch people gawk at his masterpiece in real time, said 90 percent of the content incorporates a human element - with dancers, acrobats and actors flitting around the screen.
"It's just amazing how many people come flocking to this thing with smiles on their faces," he said. "To capture the 20-second audience in transit, and get a smile on their face ... is unbelievably rewarding."
Rob Hessler was walking pretty quickly through the building to get to the subway below when the video wall stopped him in his tracks, an experience shared by others coming to the Comcast Center to visit its food court or outdoor cafe.
"It's pretty amazing. I'll probably bring my kids here," Hessler said.
Though there is little in the way of seating in the lobby, many come just to stand and stare at the screen.
"We went for this because we wanted to create something that would be very high-technology in our building that would communicate the high-technology business that we're in," Rudnay said. "When you go into lots of media companies, very often you see televisions in their lobbies - big screens with network content on it. We thought that we wanted to do something more sophisticated than that."
The tower has brought life to a rather dull section of downtown dominated by office buildings, Levitz said.
"And now there are thousands of people coming in to see the wall, shop, to (visit) the cafe, fountain, or just hang around," Niles said.
The screen is fully automated and runs about 18 hours a day, seven days a week.
Niles, with a show-biz background, is constantly creating new material - hoping to have holiday-themed sequences this fall, and updated sports-related content for Philadelphia teams.
"There's a certain thing that people would expect to see up on a screen like that," Niles said. "And we've gone to great lengths to create the unexpected."
