Views of cruise ships in Port of Barcelona from the Montjuic Castle old military fortress on Montjuic Mountain overlooking the city, Barcelona, Catalonia, Spain, Europe

View of the busy port city of Dakar, Senegal, West Africa, Africa

View of the busy port city of Dakar, Senegal, West Africa, Africa

View of the busy port city of Dakar, Senegal, West Africa, Africa

A view of the industrial and militarized Russian seaport city of Murmansk on the northern shore of the Kola Peninsula, Murmansk Oblast, Russia, Arctic, Europe

A view of the industrial and militarized Russian seaport city of Murmansk on the northern shore of the Kola Peninsula, Murmansk Oblast, Russia, Arctic, Europe

View of Kavala port from elevated position, Dimos Kavalas, Eastern Macedonia and Thrace, Gulf of Thasos, Gulf of Kavala, Thracian Sea, Greece, Europe

A view of the industrial and militarized Russian seaport city of Murmansk on the northern shore of the Kola Peninsula, Murmansk Oblast, Russia, Arctic, Europe