Baltimore's housing department estimates it has about 30,000 abandoned structures and lots throughout the city, many of them in such poor condition that they are fire and safety hazards. The city owns about a third of them, and has been taking steps to redevelop many of the properties. But how? What interesting things could these spaces be used for? By posting a template image of an empty lot between two buildings on Flickr, Baltimore's Office of Promotion & the Arts has been soliciting ideas on how to use these urban spaces from artists, architects and other creative minds. Since January, more than 55 people have posted their ideas on the site. The suggestions have been mostly green, such as buildings using sustainable materials and parks and gardens, but also have included such off-the-wall suggestions as a waterfall and a firepit. While the Infill Survey wasn't intended to lead directly to development, it was meant to spark a conversation in the community about how these spaces could be used.