The courtyard in the Northern Liberties Piazza apartment complex was meant to be a vibrant community hangout and event venue, but has degenerated into a big empty space with a giant TV on one wall. The current owners are trying something new with the Piazza Pod Park on the open lot across the street at 2nd and Germantown. Food, drink and retail outlets, and even a small gym, are housed in shipping containers. There is an enclosed eating area with an open roof deck, in addition to tables available throughout.
I went on the official opening day. It was not too crowded while I was there, but a lot of families with young children were having a good time.
And there is this sculpture called Bebot originally at Burning Man. Seeing it here is the closest I will ever get to Burning Man.
That Philly Life: Urban Exploring in Philadelphia 