Pulse, a snaking public art piece linked to the Dilworth Park fountain in Philadelphia, will soon be showing commuters what’s going on underneath their feet. The fountain sits in front of Philadelphia City Hall in Center City, and sculptor Janet Echelman will soon be realizing a light-and-mist installation that will track underground SEPTA trains in real time, thanks to a $325,000 grant from the William Penn Foundation.

The project was originally commissioned in 2009 by the Center City District Foundation (CCD), and major pieces of its foundations were embedded in the surrounding plaza when the park’s fountain was built in 2014. Pulse, described as “a living X-ray of the city’s circulatory system” by the artist, would create four-foot-tall walls of colored mist that track the trains passing below, specifically, the green, orange, and blue lines. Separate tracks of light embedded in the concrete would project into an atomized mist to create the kinetic effect. Echelman worked closely with the park’s architects, OLIN, to integrate Pulse’s infrastructure into the plaza redesign.’

The $325,000 grant that the CCD announced last Monday will cover the construction of Pulse’s green section, which would follow SEPTA’s underground green line trolley. The installation of that phase will come to life this July, though the CCD is still seeking funding for the remaining orange and blue line tracks.

The project was conceived as a tribute to Philadelphia’s first water pumping station, and Echelman was brought on board to design the piece back in 2010. However, the CCD has been trying to drum up the $4 million required to complete and maintain Pulse ever since it was announced (though a $20,000 National Endowment of the Arts grant awarded last year helped to get the ball rolling).