Long after business hours, two women are dancing on a ledge 20 feet up inside the Comcast Center. People outside stop and watch through the windows. The next day, the sun-drenched lobby sees more people pause — 400 in a single lunch hour — to see the moon rise in an inky sky. Architect Robert A.M. Stern said his masterpiece — the icy glass monolith that headquarters Comcast — would be a place “for all Philadelphia,” but it’s this, David Niles’s 84-foot-wide LED screen featuring the dancing ladies (and striking landscapes, sundry Philadelphia icons and imposing space scenttes), that literally draws the city in. Already the months-old piece, with 281 trillion colors and a resolution even better than IMAX, has captured our modern moment, intriguing and connecting viewers in a way that suggests what we’re really looking at is the new face of public art in Philadelphia. Sorry, Rocky.