The Redevelopment Authority of Philadelphia (RDA) is undergoing an overhaul by the administration of Mayor Michael Nutter, aimed at making its inventory and dispoal policies more transparent and accessible to the public. The state-chartered entity, which has the power of eminent domain and to dispose of property for less than market-value, has conveyed thousands of vacant properties over the past few decades to individuals, companies, and organizations. Most have been redeveloped — but not all. The map below shows about half of all properties (data source errors currently make a complete list impossible) which were conveyed by the RDA since 1986, but remain vacant today. Please note: many approved redevelopment projects consisted of the acquisition of vacant lots as private side yards, which still show up as "vacant."