From their Facebook Page: 
Located underneath the Market/Frankford Line (The El) in Philadelphia's Fishtown neighborhood, this rotating collection of murals aims to brighten up the Front St corridor.

The walls also serve as an outlet for many of Philadelphia's street artists to submit designs and legally display their work on a large, urban canvas. This unique gallery will rotate every six months, featuring new artists who are either experienced veterans of the urban mural scene, or are displaying their work on this scale for the first time.

Follow their Instagram for the latest updates and more photos: http://www.instagram.com/frontstreetwalls

Share and tag your photos of the walls: @FrontStreetWalls, #FrontStreetWalls