Between the 1^st century AD and the late 3^rd / early 4^th century,

Felicitas Iulia Olisipo produced and exported large quantities of fish products - such as

garum, a fermented fish sauce, widely appreciated. A large number of the production units of fish based products were located in the city's production complex, near the river, between the present-day location of Casa dos Bicos and the Pombaline Downtown. During the archaeological interventions, as part of the study and valuation of the Cerca Velha (or Moorish Wall), a south-facing wall was discovered that belonged to one of these fish products units. The wall displayed marks of remodelling and spatial changes, evidence of the era's dynamic fish production. These remains joined the already known annexes and tanks used for salting fish and preparing fish sauce (

cetariae). In addition to these findings, there is also a segment of wall, 59 feet long and 10 to 14 feet thick, built in the late 3^rd century (partly from reused architectural elements), which includes the remains of a semi-circular tower. Part of these remains can be visited in the Caso dos Bicos Archaeological Nucleus.