A zoning permit has been filed for a vertical extension atop a multi-story pre-war factory loft at at 330-48 North 12th Street (also known as 330-340 North 12th Street), just north of Center City in the up-and-coming Rail Park District in North Philadelphia. The three-story extension would rise above the lower, five-story wing of the sprawling, seven-story structure situated between North 12th Street to the east, Carlton Street to the south, and Callowhill Street to the north. The proposal is the latest addition to a rapidly-growing neighborhood around the elevated Rail Park, where an abandoned railroad turned into a public space has often been likened to Philadelphia’s answer to New York City’s ever-popular High Line.