A relatively small area just north of Center City is seeing a burst of building activity, as developers look to capitalize on walkability to the central business district's strong office market.

From Broad Street in the east to 18th Street in the west, and from Race Street in the south to Spring Garden Street in the north, 1,500 residential units were counted by the 2010 census. 1,366 new units are under construction as of this writing, which would nearly double the residential density of the area, according to the Philadelphia Inquirer.

The biggest influx of units will be from the 500-unit residential complex being built by Community College of Philadelphia adjacent to its academic building on Spring Garden. The 11-story tower will be a mix of student and non-student housing.

Also in the works is PMC Property Group's renovation of GlaxoSmithKlein's former HQ, to be turned into a mixed office and residential tower. That project, to be called One Franklin Tower, promises to deliver 360 housing units. [Philly]