Pocket parks are frequently created on a single vacant building lot or on small, irregular pieces of land. They also may be created as a component of the public space requirement of large building projects.
Pocket parks can be urban, suburban or rural, and can be on public or private land. Although they are too small for physical activities, pocket parks provide greenery, a place to sit outdoors, and sometimes a children’s playground. They may be created around a monument, historic marker or art project.
In highly urbanized areas, particularly downtowns where land is very expensive, pocket parks are the only option for creating new public spaces without large-scale redevelopment. In inner-city areas, pocket parks are often part of urban regeneration plans and provide areas where wildlife such as birds can establish a foothold. Unlike larger parks, pocket parks are sometimes designed to be fenced and locked when not in use.
[from Wikipedia, Susan Lloyd]