Recent years have witnessed a growing scholarlyinterest in ancient seaports, which consequentlyhave become a research category of their own. Portcities are seen as a specific class of city: in ageographical perspective, ancient cities weretopographically and administratively self-containedsettlements with large populations which were basedupon specialization, division of labour and socialdifferentiation. The city functioned therefore as acentral focus for its surroundings in economic butalso in political, administrative, religious andcultural terms. These different functions led to amanifoldness of the urban fabric. Port cities areadditionally characterized by their geographicalposition at the waterfront and by the spatial andeconomic symbiosis between port and city. Becauseships provided the most convenient means oftransport, port cities served as communication nodesbetween terrestrial and maritime networks, and werethus the focus of supra-regional trade linksconnecting the local with the global. Beingdestinations for immigrants, they became religiousmelting pots with growing populations who demandedcommodities, foodstuffs and services. In view ofthis, it has been assumed that port societies sharedsimilar religious, social and economic structures.It is further argued that port cities weresufficiently distinctive to form a specific urbantype, with the implicit assumption that they wereall shaped by identical developments and settings.The aim of this chapter is to scrutinize thisunderlying assumption of uniformity by focusing on asocially, religiously and economically importantphenomenon of Roman port societies, the collegia, and their socialintegration.