Maritime heritage structures, such as cranes or warehouses, are typical for historical port cities around the world and many of them have received recognition as having Outstanding Universal Value (OUV) and have been listed as UNESCO World Heritage sites. They have often been preserved and revitalized as expressions of former shipping networks and urban power after containerization in the 1960s when modern ports moved out of their historic inner-city locations to urban peripheries. We manually checked 1121 abstracts of world heritage sites published on the UNESCO World Heritage Centre website, exploring a group of words describing the typology of buildings and structures associated with port functions and activities. We found 107 World Heritage Sites (out of 1121) related to port cities. By analysing the abstracts of the 107 sites, we established a series of findings. Firstly, the concepts of port city and port heritage reflected in the abstracts do not align with the definitions given by encyclopaedias or by people interested in port city research. Secondly, the listed port heritage sites appear to emphasize three port city functions: maritime trade, defence and colonial practices. Thirdly, the listed world heritage sites present a culture-nature dichotomy in the testified OUV.