Originally, like the neighboring towns, currently located more than 5km (3.10mi) from the shore, Aveiro was a seaport. The small medieval city developed remarkably in the 15th and 16th centuries thanks to cod fishing. . In 1575, a violent storm closed the lagoon and the port silted up which declined the city.

In 1808, between the dykes built using stones from the city walls, the pass between the estuary and the ocean was successfully reopened. The ceramic and porcelain industry is developing. With prosperity comes influence: Aveiro becomes a center of Baroque art. Its school of sculpture is renowned; the city is covered with many monuments.

Aveiro was also the Portuguese capital of salt; in the traditional boats ("the moliceiros"), the seaweed was collected and then used to fertilize the dunes surrounding the Ria. Statues erected bear witness to this period.