A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Usually situated on a sea coast or estuary, ports can also be found far inland, such as Hamburg, Manchester and Duluth, with access to the sea via river or canal. Because of their roles as ports of entry for immigrants, many port cities, such as London, New York, Shanghai, Los Angeles, Singapore and Vancouver, have experienced dramatic multi-ethnic and multicultural changes.