Chicago's Urban Holes

Every city had holes in its urban fabric; lots where development occurred at one point and then, for whatever reason, buildings were demolished at a later date. Such holes can also be caused by things that are out of place in a pedestrian city - like highway interchanges or projects - that required the demolition of buildings. These holes are particularly sad when they occur in high-density areas, and go for a long time without being filled. Some have found use as parking lots, or alternatively, nearby industries or other businesses have found uses for them (usually storage or truck parking). Chicago has many of these sites all over the city, but I'd like to compile a list of the most pressing ones, and suggest uses for the site that don't include parking or storage. So - identify and suggest!>