These cities are Bremen and Bremerhaven . The state of Bremen consists of two separated enclaves : Bremen , officially the ` City ' ( Stadtgemeinde Bremen ) which is the state capital , and the city of Bremerhaven ( Stadt Bremerhaven ) . Both are located on the River Weser ; Bremerhaven is further downstream and serves as a North Sea harbor ( the name means `` Bremen 's harbor '' ) .