Ma'anar ƙamus na jimlar "Birnin Gada" birni ne da ke da gadoji masu yawa da suka ratsa kan magudanan ruwa, koguna, ko kwaruruka. Ana amfani da kalmar sau da yawa don kwatanta garuruwan da aka sani da gadoji masu kyau, irin su Pittsburgh, Pennsylvania, wanda wani lokaci ake kira "Birnin Bridges" saboda yawancin gadoji a kan kogin Allegheny, Monongahela, da Ohio Rivers. Sauran garuruwan da ake kira "Birnin Bridges" sun hada da Venice, Italiya, wadda ta shahara da hadaddun hanyoyin sadarwa na magudanar ruwa da gadoji, da kuma St. .