The long-anticipated art installation, Pulse, which will eventually see orange, blue, and green mist run through Dilworth Park, is opening its first phase next month.

On September 12, the Center City District (CCD) will unveil the trolley line portion of the project—four-foot columns of green mist will run through Dilworth Park every time the SEPTA trolley runs underground.

The project, designed by sculptor Janet Echelman, was commissioned in 2009 and has been in the works since Dilworth Park’s major 2014 renovation. The infrastructure for the installation was put in place, along with the park’s fountain, but a lack of funding put the project on hold.

It wasn’t until a $325,000 grant from the William Penn Foundation earlier this year that the project was able to move forward. The grant funds merely the trolley line part of the installation. The next two phases, which include blue mist for the MFL, and orange for the Broad Street Line, are still awaiting funding.

The CCD says the project was inspired by the city’s “historic associations with both water and transportation.”

To get a better idea of what the project will look like, check out the CCD’s video below: