The setting sun gilds four of Pittsburgh's many bridges as seen in this photo from Mount Washington. Not everyone knows that one of the city's nicknames is "City of Bridges". There are over 400 bridges of all types (except for bridges that open) within the city itself and more than 2000 in the area. A cruise under the 29 bridges spanning the city's famous three rivers is a treat for engineers who want to check out the varying kinds, but there are also major bridges across valleys and ravines.