From BR Wiki:
Proudglaive: Proudglaive is a city of ten thousand citizens. Proudglaive is also a port city, located on the deep Spider River, and even large ocean-going vessels can be seen tied up at its wharves. Michael Agnelie is the city’s lord mayor, although he reports to the castellan in nearby Blacktower Castle.
Proudglaive lies on the farthest point of the Spider River that is navigable by ocean-going vessels, and many docks and wharves line the riverfront. The meat, produce, wool and leather of the local farmlands find their market here. With a budding middle class, Proudglaive also offers services of craftsmen and experts not found in other parts of the barony.
Is this true for RoE? Not that I'd start with an already built port in Caercas (I'm not munchkiing), but that it would be possible to build one there?